MINING  AND  MANUFACTURE 

OF 

FERTILIZING  MATERIALS 

AND 

THEIR  RELATION  TO  SOILS 


BY      t 

STRAUSS  L.  LLOYD,  E.M. 


IL  L  USTKA  TED 


NEW   YORK 

D.  VAN   NOSTRAND   COMPANY 

25  PARK  PLACE 

1918 


Copyright,   1918 

BY 
D.   VAN    NOSTRAND    COMPANY 


PRESS    OF 

BRAUNWORTH    &    CO. 

BOOK    MANUFACTURERS 

.BROOKLYN.    N.    V. 


PREFACE 


IT  is  to  be  hoped  that  the  present  volume 
has  unique  merits  of  its  own,  and  will  appeal 
not  only  to  manure  manufacturers  but  to 
farmers,  as  well  as  to  agricultural  students  and 
all  those  who  take  an  intelligent  interest  in  the 
subject  of  agricultural  chemistry.  Common 
sense  dictates  that  it  is  equally  important  for 
the  student  of  agriculture  to  be  ab'e,  if  need 
be,  to  effect  the  synthesis  of  a  manure  as  to  be 
able  to  carry  out  the  analysis  thereof.  The  student 
who  can  construct,  mentally,  a  formula  for  a 
manure  to  yield,  whether  by  dry  mixing  or  wet 
mixing,  certain  predetermined  results  on  analysis, 
is  more  highly  trained  than  he  who  can  use 
the  faculties  of  destruction  to  resolve  a  manure 
into  its  constituent  e'ements  by  following  a 
treatise  on  agricultural  chemical  analysis,  and 
that  too  often  by  methods  which  he  would  have 
to  unlearn  if  he  entered  a  fertilizer  factory, 
where  he  would  have  to  analyze  manures  and  raw 
materials  against  chemists  of  some  reputation. 

STRAUSS  L.  LLOYD. 

INVERNESS,  FLORIDA, 
July  15,  1918. 


111 


385547 


CONTENTS 


CHAPTER  I 
Chemistry  of  Fertilizers 

PAGE 

The  Four  Fundamental  Laws — Nitrogen — Potash — Phos- 
phoric Acid — Lime — Terms  Used  in  Analyses — Loss  of 
Fertilizer  in  Soils — Indirect  Fertilizers — Direct  Ferti- 
lizers    1 

CHAPTER  II 
Origin  and  Composition  of  Soils 

Origin  of  Soil — Geologically  Considered — Chemical  Ele- 
ments Present — Non-metals — Metals 15 

CHAPTER   III 
The  Relation  Between  Soils  and  Fertilizing  Materials 

Exhaustible  Elements  and  Non-exhaustible  Elements — 
Preference  Shown  by  Plant  Life — Separate  Fertilizing 
Ingredients — Economy  in  Separate  Ingredients 30 

CHAPTER   IV 

Pebble  Phosphate  Ore  Dressing  and  Milling 
Steam  Shovels  and  Hydraulic  Mining  Practice 37 

CHAPTER  V 
Hard  Rock  Phosphate  Ore  Dressing  and  Milling 

Loss  of    Soft  Ores — Separating  the  Ores  from  Clays,  etc., 

and  Process  of  Roasting  or  Drying 43 


vi  CONTENTS 

CHAPTER  VI 
Phosphorus 

PAGE 

Origin  of  Phosphate  Rock,  Basic  Slag,  Bone  Meal,  Ammo- 
nium Sulphate,  Sodium  Nitrate,  Organic  Nitrogenous 
Materials,  Potash  and  Guano 52 

CHAPTER  VII 
Artificial  Manure  Manufacture 

Phosphatic  Manures — Mineral  Phosphates — Superphos- 
phates— Precipitated  Phosphates — Mixed  Manures.  .  60 

CHAPTER  VIII 
Manufacture  of  Superphosphate 67 

CHAPTER  IX 
Compound  Manures 77 

CHAPTER  X 
Nitrogenous  Manures 87 

CHAPTER  XI 

The  Fixation  of  Atmospheric  Nitrogen,  Manufacture  of 
Cyanamide  and  Nitrate  of  Lime.  Experiments  with 
Cyanamide 95 

CHAPTER  XII 

Potassic  Manures.  Manufacture  from  Crude  Salt.  Manu- 
facture from  Feldspar.  Manufacture  from  Sunflower 
and  Kelp  Plants 101 

CHAPTER  XIII 

On  the  Examination  of  Commercial  Fertilizers  and  Ma- 
terials   126 

CHAPTER  XIV 
On  the  Examination  of  Soils.  .  .139 


MINING  AND  MANUFACTURE  OF 
FERTILIZING  MATERIALS 


CHAPTER  I 
CHEMISTRY   OF  FERTILIZERS 

The  Four  Fundamental  Laws — Nitrogen — Potash — Phos- 
phoric Acid — Lime — Terms  Used  in  Analyses — Loss  of 
Fertilizer  in  Soils — Indirect  Fertilizers — Direct  Ferti- 
lizers. 

THE  systematic  scientific  study  of  agriculture 
was  commenced  about  sixty  years  ago,  and  it 
is  to  the  celebrated  German  agricultural  chem- 
ist Justus  von  Liebig  that  we  owe  the  following 
four  elementary  laws,  which  are  the  foundation 
of  the  best  modern  practice. 

I.  A  soil  can  be  termed  fertile   only   when   it 
contains  all  the  materials  necessary  for  the  nu- 
trition  of  plants,    in   the   required   quantity,   in 
the  proper  form. 

II.  With  every  crop,  a  portion  of  these  ingre- 
dients is  removed.     A  part  of  this  is  again  added 
from  the  inexhaustible  store  of  the  atmosphere; 
another   part,    however,    is   lost   forever   if   not 
replaced  by  man. 


2,      MANUFACTURE  OF  -FERTILIZING  MATERIALS 

III.  The    fertility    of    the    soil     remains    un- 
changed if  all  the  ingredients  of  the  crops  are 
given   back   to   the   soil.     Such   a  restitution   is 
effected  by  manure  or  fertilizers. 

IV.  The  manure  produced  in    the    course    of 
farming  is  not  sufficient  to  maintain  permanently 
the  fertility  of  a  farm;   it  lacks  the  constituents 
which  are  annually  sold    in  the  shape  of  grain, 
hay,  milk,  and  live  stock. 

These  laws  cover  the  whole  subject,  but  to 
understand  them  so  that  they  may  be  applied 
at  work  in  the  field,  it  is  necessary  to  have  a 
fair  idea  of  the  sources  of  plant  food  of  the  dif- 
ferent kinds,  and  how  best  to  use  these  different 
kinds  for  different  crops. 

It  is  generally  understood  that  all  manures 
or  fertilizers  are  valuable  for  the  nitrogen,  potash, 
and  phosphoric  acid  they  contain.  Though  other 
substances  are  needed  for  plant  growth,  they  are 
almost  always  present  in  the  soil  in  sufficient 
quantity.  Lime  might  be  made  an  exception, 
although  its  use  is  largely  to  improve  the  me- 
chanical condition  of  the  soil,  and  cure  it  of 
sourness.  Lime  also  aids  in  rotting  the  vege- 
table matter. 

The  influence  of  nitrogen  in  its  various  forms 
upon  plant  growth  is  shown  by  at  least  three 
striking  effects.  The  growth  of  stem  and  leaves 
is  greatly  promoted,  while  that  of  buds  and 
flowers  is  retarded.  Ordinarily,  most  plants,  at 
a  certain  period  of  growth,  cease  to  produce 


CHEMISTRY  OF  FERTILIZERS  3 

new  branches  and  foliage,  or  to  increase  those 
already  formed,  and  commence  to  produce  flowers 
and  fruits,  whereby  the  species  may  be  perpet- 
uated. If  a  plant  is  provided  with  as  much 
available  nitrogen  as  it  can  use  just  at  the  time 
it  begins  to  flower,  the  formation  of  flowers  may 
be  checked,  while  the  activity  of  growth  is  trans- 
ferred back  to  and  renewed  in  stems  and  leaves, 
which  take  on  a  new  vigor  and  multiply  with 
luxuriance.  Should  flowers  be  produced  under 
these  circumstances,  they  are  often  sterile  and 
produce  no  seed. 

The  next  effect  of  nitrogen  upon  plants  is 
to  deepen  the  color  of  the  foliage,  which  is  a 
sign  of  increased  vegetative  activity  and  health. 
Another  effect  of  nitrogen  is  to  increase  in  a 
very  marked  degree  the  relative  proportion  of 
nitrogen  in  the  plant. 

Potash  is  essential  to  the  formation  and  trans- 
ference of  starch  in  plants.  Starch  is  known 
to  be  first  formed  in  the  leaves  of  plants,  after 
which  in  some  unknown  way  it  becomes  soluble 
enough  within  the  plant  cells  to  enable  it  to  pass 
through  the  cell-walls  gradually  and  later  to 
be  carried  into  the  fruit,  where  it  accumulates 
and  changes  back  to  its  insoluble  form.  It  is 
well  established  that  potash  is  intimately  con- 
nected with  the  formation  of  starch  in  the  leaves 
and  with  its  transference  to  the  fruit.  No  other 
element  can  take  the  place  of  potash  in  perform- 
ing this  work.  Potash  is  important  on  account 


4         MANUFACTURE  OF  FERTILIZING  MATERIALS 

of  its  influence  upon  the  development  of  the 
woody  parts  of  stems  and  fleshy  portions  of  fruits. 

Experiments  have  shown  that  plants  will  die 
before  reaching  maturity  unless  they  have  phos- 
phoric acid  to  feed  upon.  Phosphates  appear 
to  perform  three  distinct  functions  of  plant  life. 

They  aid  in  the  nutrition  of  the  plant  by 
furnishing  the  needed  quantities  of  phosphoric 
acid. 

They  aid  the  plant,  in  some  way  not  well 
understood,  to  make  use  of  or  assimilate  other 
ingredients.  Phosphates  are  found  in  the  seeds 
of  plants,  and,  as  already  stated,  a  plant  does 
not  come  to  maturity  and  so  does  not  produce 
seeds,  unless  phosphates  are  present  in  the  soil 
for  the  plants  to  feed  upon.  The  liberal  applica- 
tion of  available  phosphate  compounds  appears 
to  hasten  the  maturity  of  plants. 

Certain  forms  of  phosphates  render  the  al- 
buminoids sufficiently  soluble  to  enable  them  to 
be  carried  from  the  growing  parts  of  plants  to 
the  seeds,  in  which  they  accumulate  in  quantity. 

The  chief  function  of  lime  is  to  improve  the 
mechanical  condition  of  the  soil  by  loosening 
heavy  clay  soils  and  also  by  holding  together 
and  giving  body  to  light  sandy  soils.  Lime  aids 
in  the  decomposition  of  animal  and  vegetable 
matter,  such  as  vegetable  mould,  stable-manure, 
etc.,  and  tends  to  convert  them  into  available 
plant  food. 

In  using  lime,  care  should  be   taken    not    to 


CHEMISTRY  OF  FERTILIZERS  5 

use  too  large  quantities  at  a  time;  and,  ordi- 
narily, it  is  best  to  use  it  in  connection  with  a 
liberal  application  of  nutritive  fertilizers.  Lime 
can  be  used  with  much  advantage  on  freshly 
drained  swamp-lands  and  also  on  lands  newly 
cleared. 

Fertilizer  dealers  and  manufacturers  treat  the 
different  forms  of  fertilizers  and  fertilizer  materials 
separately,  and  it  is  important  that  one  should 
be  familiar  with  these  trade  names,  and  under- 
stand what  they  mean. 

The  following  list  contains  most  of  the  terms 
used  in  stating  fertilizer  analyses. 

Nitrogen  is  expressed  as:  (A)  Nitrogen, 
(B)  Ammonia,  (C)  Nitrogen  equal  (or  equivalent) 
to  Ammonia. 

Phosphoric  Acid  is  expressed  as:  (A)  Phos- 
phoric Acid,  (B)  Soluble  Phosphoric  Acid,  (C) 
Reverted  Phosphoric  Acid,  (D)  Precipitated  Phos- 
phoric Acid,  (E)  Available  Phosphoric  Acid, 
(F)  Soluble  and  Available  Phosphoric  Acid,  (G) 
Insoluble  Phosphoric  Acid,  (H)  Total  Phosphoric 
Acid,  (7)  Phosphoric  Acid  equal  (or  equivalent) 
to  Bone  Phosphate  of  Lime. 

Potash  is  expressed  as:  (A)  Potash,  (B) 
Potash  (actual),  (C)  Potash  S.  (or  Sul.),  (D) 
Potash  (Soluble),  (E)  Potash  as  Sulphate,  (F) 
Potash  equal  (or  equivalent)  to  Sulphate  of 
Potash,  (G)  Sulphate  of  Potash,  (H)  Potassium 
Oxide. 

(A)  Nitrogen  is  a  gas,  and,  in  this  form,  can- 


6         MANUFACTURE  OF  FERTILIZING  MATERIALS 

not  be  used  in  fertilizers.  Therefore,  whenever 
we  speak  of  nitrogen  in  fertilizers,  we  do  not 
mean  that  nitrogen  exists  in  them  as  simple 
nitrogen.  The  nitrogen  in  fertilizers  is  always 
combined  with  other  elements,  and  may  be  pres- 
ent in  one  or  more  different  forms:  (1)  in  the 
form  of  nitrates,  as  nitrate  of  soda ;  (2)  in  the  form 
of  ammonia  compounds,  as  sulphate  of  ammonia; 
and  (3)  in  the  form  of  organic  matter,  animal, 
or  vegetable,  as  dried  blood,  meat,  tobacco-stems, 
etc.  Chemical  analysis,  according  to  official 
methods,  does  not  attempt  to  ascertain  and  state 
in  which  form  or  forms  the  nitrogen  is  present 
in  a  fertilizer. 

When,  therefore,  nitrogen  is  expressed  in  an 
analysis  or  guarantee  as  " nitrogen,"  it  refers 
to  the  entire  amount  of  nitrogen  present  without 
regard  to  the  particular  form  or  forms  in  which 
it  is  present. 

(B)  Ammonia  consists  of  nitrogen  combined 
with  hydrogen.  A  pound  of  nitrogen  will  form 
more  than  a  pound  of  ammonia,  because  the 
ammonia  formed  from  a  pound  of  nitrogen  will 
contain  that  pound  of  nitrogen  plus  the  necessary 
amount  of  hydrogen  added  to  form  ammonia. 
The  chemical  relations  of  nitrogen  and  ammonia 
are  such  that  14  pounds  of  nitrogen  will  unite 
with  exactly  three  pounds  of  hydrogen,  and  will, 
therefore,  produce  just  17  pounds  of  ammonia; 
or  1  pound  of  nitrogen  will  make  1.214  pounds 
of  ammonia. 


CHEMISTRY  OF  FERTILIZERS  7 

(C)  Nitrogen  equal  or  equivalent  to  ammonia 
is  a  form  of  expression  which  simply  means  that 
the  nitrogen  is  stated  not  as  nitrogen  but  as 
ammonia. 

It  would  be  better  on  every  account  if  all 
guarantees  stated  simply  nitrogen  and  never  men- 
tioned ammonia  at  all.  As  a  matter  of  fact, 
compounds  of  ammonia  are  quite  uncommon  in 
commercial  fertilizers,  because  nitrogen  in  this 
form  is  the  most  expensive  and,  therefore,  least 
used.  Strictly  speaking,  the  term  ammonia  should 
never  be  used  except  when  sulphate  of  ammonia  or 
some  similar  compound  is  present  in  the  fertilizer. 

(A)  Phosphoric    Acid,   as    used  in    connection 
with  fertilizers,  is  a  compound  containing  phos- 
phorous and  oxygen,  which  in  fertilizers  is  found 
never  by  itself,   but  in  combination  with  lime. 
Phosphoric  acid  stands  for  a  certain  amount  of 
phosphate  of  lime.     We  may  say  roughly  that 
one  part  of  phosphoric  acid  is  equivalent  to  about 
two  parts  of  phosphate  of  lime,  but  it  is  exactly 
2.1831  and  the  percentage  of  phosphoric  acid  mul- 
tiplied by  this  number  will  give  the  percentage  of 
"bone  phosphate  of  lime/'     But  we  know  that 
phosphoric  acid  exists  in  several  different  forms. 

(B)  Soluble    phosphoric    acid    represents    the 
amount  of  phosphate  of  lime  that  dissolves  easily 
in  water;   it  is  formed  by  treating  with  sulphuric 
acid    some    form    of    insoluble    lime    phosphate: 
The  phosphate  thus  formed  is.  readily  soluble  in 
water. 


8         MANUFACTURE  OF  FERTILIZING  MATERIALS 

(C)  Reverted  phosphoric  acid  is  formed  from 
soluble  phosphoric  acid  under  conditions  to  be 
explained  hereafter. 

(D)  Precipitated  phosphoric  acid  is  simply  an- 
other name  for  reverted  phosphoric  acid. 

(E)  Available   phosphoric   acid   includes   both 
the   soluble    and   reverted   form     of   phosphoric 
acid,  because  both  forms  are  available  for  the 
use  of  plants. 

(F)  Soluble  and  available  phosphoric  acid  is 
an  expression  which  means  the  same  as  avail- 
able. 

(G)  Insoluble   phosphoric   acid  represents   the 
form   of   phosphoric   acid   in   raw   phosphate   of 
lime,  and  which  is  of  least  value  for  agricultural 
purposes. 

(H)  Total  phosphoric  acid  represents  the  entire 
phosphoric  acid  compounds  without  regard  to  the 
forms  in  which  they  exist.  The  total  phosphoric 
acid  is,  therefore,  the  sum  of  the  soluble,  reverted 
and  insoluble  forms;  or,  to  state  it  in  another 
way,  the  sum  of  the  available  and  insoluble 
forms. 

(/)  Phosphoric  acid  equal  (or  equivalent)  to 
bone  phosphate  of  lime  is  an  expression  which 
usually  means  nothing  more  nor  less  than  insol- 
uble phosphoric  acid. 

(A)  Potash,  as  used  in  connection  with  fer- 
tilizers, always  means  a  compound  containing 
potassium  and  oxygen,  known  chemically  as 
potassium  oxide.  Potash  is  never  found  as  such 


CHEMISTRY  OF  FERTILIZERS  9 

in  fertilizers,  but  chemists  use  this  form  of  ex- 
pressing the  results  of  analyses  as  a  convenient 
standard  for  reference.  Fertilizers  generally  con- 
tain potash  in  such  forms  as  sulphate  of  potash, 
muriate  of  potash,  or  carbonate  of  potash.  In- 
stead of  stating  the  amount  of  sulphate,  muriate, 
or  carbonate  of  potash  in  a  fertilizer,  its  equivalent 
amount  is  stated  only  in  the  form  of  actual  potash 
in  giving  the  results  of  analyses. 

(B)  Potash  actual  is  simply  another  name  for 
potash,  as  distinct  from  sulphate,  muriate,  etc. 

(C)  Potash    S.    (or    Sul.)    means   sulphate   of 
potash.     This  is  quite  often  used  by  manufac- 
turers in  giving  guarantees. 

(D)  Potash   soluble   represents  the  amount  of 
potash  that  dissolves  in  water  and  is  available 
for  the  use  of  plants.     The  different  forms  of 
potash  commonly  used  in  fertilizers  are  readily 
soluble  in  water,  otherwise  they  would  not  be 
available  for  the  use  of  plant  life. 

(E)  Potash  as  sulphate  means  simply  sulphate 
of  potash. 

(F)  Potash  equal   (or  equivalent  to  sulphate 
of  potash)  is  an  expression  which  means  simply 
sulphate  of  potash. 

(G)  Sulphate  of  potash  signifies  that  this  com- 
pound is  actually  present  in  the  fertilizer,  and 
that  there  is  no  muriate  of  potash  present. 

(H)  Potassium  oxide  means  the  same  as  potash, 
or  actual  potash. 

The  phosphoric  acid  in  raw  materials  such  as 


10      MANUFACTURE  OF  FERTILIZING  MATERIALS 

ground  bone  or  ground  phosphate  does  not  readily 
leach  out  of  the  soil.  In  specially  prepared 
materials,  however,  like  dissolved  bone  or  dis- 
solved phosphate  (acid  phosphate)  the  phosphoric 
acid  is  quite  soluble  and  would  be  removed  from 
the  soil  by  drainage  water,  were  it  not  for  the 
fact  that  immediately  after  application  the  phos- 
phoric acid  becomes  changed  into  another  form, 
which  is  not  apt  to  leach  away. 

The  mineral  forms  of  nitrogen,  such  as  nitrate 
of  soda  and  sulphate  of  ammonia,  both  dissolve 
easily  in  water,  hence  they  would  soon  wash  into 
the  subsoil  and  out  of  reach  of  the  plants.  The 
so-called  organic  forms  of  nitrogen,  like  cotton- 
seed-meal, tankage,  fish-scrap,  dried  blood,  etc., 
are  less  soluble,  and  experience  indicates  that  they 
are  largely  retained  in  the  soil.  It  is  a  matter  of 
observation  also  that  there  is  little  loss  of  nitro- 
gen by  drainage  when  the  soil  is  covered  with 
vegetation,  because  the  roots  of  the  growing 
plants  absorb  nitrogen  very  readily. 

Potash,  it  has  been  found  by  experience,  does 
not  wash  away  to  any  appreciable  extent,  because 
it  forms  certain  combinations  in  the  soil  which  are 
not  so  soluble,  but  which  at  the  same  time  are 
readily  available  to  the  growing  crops. 

In  addition  it  may  be  said,  in  general,  that  loss 
of  plant  food  is  greatest  in  sandy  soils;  the  coarser 
the  sand,  the  greater  the  loss,  the  other  con- 
ditions being  the  same.  Clay  and  humus  have 
very  marked  power  in  retaining  plant  food. 


CHEMISTRY  OF  FERTILIZERS  11 

A  stimulant  or  indirect  fertilizer  is  one  which 
does  not  in  itself  furnish  directly  to  the  soil  any 
needed  plant  food,  but  whose  chief  value  depends 
upon  the  power  it  possesses  of  changing  unavail- 
able into  available  forms  of  plant  food.  The  stim- 
ulant or  indirect  fertilizers  which  have  been  most 
commonly  employed  are  lime,  gypsum,  and 
common  salt  or  sodium  chloride. 

Gypsum,  or  land-plaster,  known  chemically  as 
calcium  sulphate,  or  sulphate  of  lime,  in  some 
manner  aids  the  process  of  nitrification,  by  which 
ammonia  and  the  nitrogen  of  organic  matter  are 
converted  into  nitric  acid  and  nitrates.  It  also 
acts  upon  the  insoluble  forms  of  potash  and  other 
elements  of  plant  food,  converting  them  into 
soluble  and  available  forms;  it  is  of  value  on 
certain  soils  to  certain  crops,  such  as  clover,  peas, 
lucerne  and  similar  plants. 

Quick  or  burnt  lime,  or  calcium  oxide,  com- 
monly called  lime,  produces  changes  in  both  the 
physical  and  the  chemical  character  of  soils. 
Freshly  burned  lime  acts  chemically  upon  soils 
by  decomposing  vegetable  and  mineral  matter 
present  in  the  soil  and  changing  them  into  forms 
which  are  available  as  food  for  plants.  Thus 
lime  acts  upon  insoluble  mineral  substances  con- 
taining potash,  etc.,  and  converts  them  into 
soluble  forms.  Lime  aids  in  the  decomposition 
of  animal  and  vegetable  matter,  such  as  vegetable 
mould,  stable-manure,  etc.,  and  tends  to  con- 
vert them  into  available  plant  food.  In  using 


12       MANUFACTURE  OF  FERTILIZING  MATERIALS 

lime,  care  should  be  taken  not  to  use  too  large 
quantities  at  a  time,  and,  ordinarily,  it  is  best 
to  use  it  in  connection  with  a  liberal  application 
of  nutritive  fertilizer.  Lime  can  be  used  to  ad- 
vantage on  freshly  drained  swamp-lands  and  also 
on  lands  newly  cleared. 

The  explanation  of  the  chemical  action  of  lime 
on  soils  may  be  in  order  here.  Before  nitrogen  in 
ammonium  sulphate  or  organic  substances  can  be 
taken  up  by  plant  life,  it  must  be  converted  into 
nitrates.  The  nitrogen  in  organic  substances  is 
chiefly  in  an  albuminoid  form.  The  first  de- 
composition which  such  substances  undergo  re- 
sults in  the  production  of  ammonia.  The  oxida- 
tion necessary  for  the  conversion  of  ammonia 
into  nitric  acid  is  dependent  upon  the  presence 
of  a  so-called  "nitrifying"  organism,  which  is 
a  bacillus  to  which  the  name  of  "nitromonas" 
has  been  assigned.  The  organism  requires  the 
usual  mineral  constituents,  e.g.,  phosphates,  for 
its  growth,  and  free  access  of  air,  on  which  account 
it  is  not  active  in  the  ground  at  a  greater  depth 
than  six  feet.  The  formation  of  nitrates  appears 
to  be  always  due  to  the  action  of  the  same  or- 
ganism; nitrites,  on  the  other  hand,  are  pro- 
duced by  several  different  species,  which  vary 
with  the  locality.  In  order  that  all  the  ammonia 
may  be  converted  into  nitric  acid,  a  fixed  base 
must  be  present,  like  lime,  otherwise  ammonia 
nitrate  is  the  final  product.  The  temperatures 
between  which  the  organisms  can  act  are  3  and 


CHEMISTRY  OF  FERTILIZERS  13 

55  degrees  C.,  37  degrees  C.,  being  that  at  which 
they  are  most  active.  Darkness  is  favorable 
to  their  development.  The  process  of  nitrifica- 
tion is  but  one  phase  of  the  general  oxidizing 
action  which  is  associated  with  the  growth  of 
these  bacilli.  Thus  they  are  capable  of  converting 
iodides  into  iodates.  "  Denitrifying "  organisms 
appear  also  to  exist  in  the  soil,  capable  of  reducing 
nitrate  even  to  free  nitrogen.  These  become  active 
when  the  soil  is  water-logged,  and  are  inimical  to 
plant  life. 

The  process  of  nitrification  is  so  rapid  that 
ammonium  sulphate  is  scarcely  less  readily  assim- 
ilated than  is  sodium  nitrate.  There  is,  however, 
a  certain  amount  of  difference  in  the  quantity 
of  certain  crops  when  manured  with  nitrate  and 
ammonium  sulphate  respectively,  which  will  be 
found  as  set  forth.  Another  difference  in  their 
action  is  on  the  soil  itself;  before  the  nitrifica- 
tion of  ammonium  sulphate  can  be  completed, 
the  sulphuric  acid  must  be  removed  by  a  base— 
e.g.,  lime — in  the  soil,  and  a  further  quantity  of 
base  will  be  required  by  the  nitric  acid  when  formed. 

Common  salt  has  an  indirect  fertilizing  value 
which  is  mainly  due  to  the  fact  that  it  has  the 
power  of  changing  unavailable  forms  of  plant 
food,  especially  potash,  into  available  forms. 

It  should  be  kept  in  mind  that  these  stimulant 
fertilizers,  that  is,  gypsum  (or  plaster),  lime,  and 
salt — are  not  used  for  the  plant  food  contained 
in  them;  hence,  as  used,  they  do  not  furnish 


14      MANUFACTURE  OF  FERTILIZING  MATERIALS 

needed  plant  food.  The  chief  value  of  their 
use  lies  in  the  fact  that  they  can  change  unavail- 
able into  available  forms  of  plant  food.  It  can 
readily  be  seen  that,  when  stimulant  fertilizers  are 
used  exclusively  for  a  term  of  years,  the  soil  each 
year  loses  nitrogen  and  phosphoric  acid,  which  are 
not  replaced.  The  inevitable  result  of  such  treat- 
ment is  the  exhaustion  of  these  important  food 
constituents  from  the  soil.  This  affords  an  explan- 
ation of  the  question  often  raised  now  as  to  why 
the  application  of  land-plaster  does  not  give 
such  results  in  crop  yields  at  present  as  in  former 
days.  When  land-plaster  was  the  only  fertilizing 
material  added  to  soils  for  years  in  succession, 
it  was  possible  to  produce  increased  crops  so 
long  as  there  were  in  the  soil  enough  compounds 
of  nitrogen,  potassium  and  phosphorus  to  be 
rendered  available  by  the  action  of  the  land- 
plaster.  When,  therefore,  these  forms  of  plant 
food  were  largely  removed,  there  was  nothing 
for  the  land-plaster  to  act  upon  in  order  to 
increase  the  supply  of  available  food  material. 
The  land-plaster  furnished  no  needed  food,  but 
simply  helped  the  crop  to  use  more  rapidly  the 
store  of  plant  food  present  in  the  soil. 

Direct  fertilizers  contain  forms  of  plant  food, 
which  contribute  directly  to  the  growth  and 
substance  of  plants.  Such  materials,  as  have 
already  been  mentioned,  contain  nitrogen,  potash, 
and  phosphoric  acid  compounds,  or  any  two,  or 
all  three  of  these  materials. 


CHAPTER  II 
ORIGIN  AND   COMPOSITION   OF   SOILS 

Origin  of  Soil — Geologically  Considered — Chemical  Elements 
Present — Non-metals —  M  etals 

THE  term  soil,  in  its  broadest  sense,  is  used 
to  designate  that  portion  of  the  surface  of  the 
earth  which  has  resulted  from  the  disintegration 
of  rocks  and  the  decay  of  plants  and  animals, 
and  which  is  suited,  under  proper  conditions 
of  moisture  and  temperature,  to  the  growth  of 
plants.  It  consists,  therefore,  chiefly  of  min- 
eral substances,  together  with  some  products  of 
organic  life,  and  of  certain  living  organisms 
whose  activity  may  influence  vegetable  growth 
either  favorably  or  otherwise.  The  soil  also  holds 
varying  quantities  of  gaseous  matter  and  of  water, 
which  are  important  factors  in  its  functions.  The 
soil  cannot  be  regarded  as  entirely  dead  matter, 
but  as  containing  living  organisms  exhibiting 
many  most  remarkable  biological  phenomena. 

Agriculturally  considered,  the  soil  proper  is  the 
older  and  more  thoroughly  disintegrated  super- 
ficial layer  of  the  earth,  which  has  been  longest 
exposed  to  weathering  and  the  influences  of 
organic  life.  It  varies  from  a  few  inches  to  several 

15 


16       MANUFACTURE  OF  FERTILIZING  MATERIALS 

feet  in  depth.  The  term  subsoil  is  usually  applied 
to  a  layer  of  soil  beginning  at  the  usual  depth  of 
cultivation  and  of  a  thickness  of  from  6  to  9  in. 
The  surface  of  demarcation  of  change  of  color  is 
sometimes  regarded  as  the  upper  superficial 
boundary  of  the  subsoil.  The  term  soil  and  sub- 
soil are  therefore  not  always  used  with  the  same 
relative  signification.  The  subsoil  is  not,  as  a 
rule,  so  thoroughly  disintegrated  as  the  soil,  since 
it  is  protected  in  a  measure  by  the  overlying 
material.  It  usually  contains  less  organic  matter 
than  the  soil.  There  is  freer  circulation  of  air  in 
the  soil  than  in  the  subsoil,  and  the  metallic  ele- 
ments usually  exists  in  the  upper  layers  as  higher 
oxides.  There  is  usually  a  notable  difference  in 
color  between  the  soil  and  subsoil,  and  frequently 
a  very  sharp  color  line  separates  the  two. 

Geologically  considered,  the  soil  is  that  portion 
of  the  earth's  crust  which  has  been  more  or  less 
thoroughly  disintegrated  by  weathering  and  other 
forces  from  the  original  rock  formations,  or  from 
the  sedimentary  rocks,  or  from  the  unconsolidated 
sedimentary  material.  The  soil  has,  therefore, 
the  same  essential  constitution  as  the  general  mass 
of  the  earth,  except  that  this  debris  has  been  sub- 
jected to  the  solvent  action  of  water  and  the 
influence  of  organic  life. 

The  chemical  elements  present  in  the  soil  are 
naturally  some  or  all  of  those  which  were  present 
in  the  original  rocks.  For  purposes  relating  to 
agriculture,  it  is  not  necessary  to  take  into 


ORIGIN  AND  COMPOSITION  OF  SOILS  17 

account  the  rare  elements  which  may  occur  in  the 
soil,  but  only  those  need  be  considered  which  are 
present  in  some  quantity  and  which  enter  as  an 
important  factor  into  plant  growth  or  modify  in 
some  manner  its  physical  properties.  Of  the 
whole  number  of  chemical  elements  less  than 
one-third  are  of  any  importance  in  soil  investi- 
gations. These  elements  may  be  grouped  into 
two  classes,  the  non-metals  and  the  metals  as 
follows : 

Non-metals.  Metals. 

Oxygen  Aluminum 

Silicon  Calcium 

Carbon       »  Magnesium 

Sulphur  Potassium 

Hydrogen  Sodium 

Chlorine  Iron 

Phosphorus  Manganese 

Nitrogen  Barium 

Fluorine  Titanium 

Boron  '  Chromium 

Oxygen  exists  in  the  free  gaseous  state  in  the 
atmosphere  of  which  it  constitutes  about  one-fifth 
by  bulk,  and  in  combination  with  other  elements 
it  forms  nearly  half  the  weight  of  the  solid  earth, 
and  eight-ninths  by  weight  of  water.  It  enters 
into  combination  with  most  of  the  other  elements, 
forming  what  are  known  as  oxides,  and  with  many 
of  the  elements  it  unites  in  several  proportions, 
forming  oxides  of  different  composition.  Com- 


18       MANUFACTURE  OF  FERTILIZING  MATERIALS 

bined  with  silicon,  carbon,  sulphur,  and  phos- 
phorus, it  forms  an  essential  part  of  the  silicates, 
carbonates,  sulphates,  and  phosphates,  most  of 
which  are  very  abundant  and  all  of  which  are  very 
widely  distributed  in  the  earth's  crust.  In  this 
form  it  is  exceedingly  stable  and  is  rarely  set  free. 
With  the  exception  of  the  oxides  of  silicon  and 
iron  these  oxides  seldom  occur  uncombined  with 
the  metals  as  constituents  of  rocks  or  soils.  The 
oxides  of  iron  very  commonly  occur  as  such  in 
rocks  and  soils,  and  play  a  very  important  part 
in  organic  life.  The  several  oxides  of  iron  very 
frequently  determine  the  color  of  soils;  as  the 
iron  is  more  or  less  oxidized,  or  as  it  is  exposed 
more  or  less  to  access  of  air,  the  color  of  the  soil 
changes.  These  oxides  of  iron  also  play  an 
important  part  in  the  absorptive  capacities  of 
soils  for  moisture  and  other  physical  conditions  of 
soils,  and  also  in  the  oxidation  of  organic  matters 
in  the  soils.  Many  organic  substances,  and  even 
the  roots  of  growing  plants  when  deprived  of 
free  access  of  air,  can  readily  secure  oxygen  from 
the  iron  oxide,  thus  reducing  the  iron  to  a  lower 
form  of  oxidation,  the  oxygen  being  used  for  the  ox- 
idation of  the  organic  matter  or  for  the  needs  of  the 
growing  plant;  while  the  lower  oxide  of  iron  can 
easily  take  up  the  oxygen  of  the  air  and  again 
be  converted  into  a  higher  oxide  ready  again  to 
give  up  a  part  of  its  oxygen  and  thus  serve  as  a 
carrier. 

Silicon  never  occurs  in  the  free  state,  but  com- 


ORIGIN  AND  COMPOSITION  OF  SOILS          19 

bined  with  oxygen  it  forms  silica,  which  consti- 
tutes free  or  in  combination,  more  than  one- 
half  of  the  earth's  crust.  The  oxide  of  silicon 
occurs  in  the  very  common  form  of  quartz,  and 
as  silicate  of  alumina,  lime  or  magnesia  silicon 
forms  an  essential  part  of  many  minerals,  such  as 
the  feldspars,  amphiboles,  pyroxenes  and  the 
micas,  besides  being  an  essential  ingredient  of 
many  other  minerals.  Silica  is  relatively  very 
slightly  affected  by  the  ordinary  forces  concerned 
in  the  decay  of  rocks,  and  even  after  the  crystals 
of  feldspars,  micas  and  other  common  minerals 
occurring  in  rocks  have  been  disintegrated  it 
remains  as  hard  grains  of  sand,  forming  the 
bulk  of  most  soils.  By  far  the  largest  part  of 
silicon  in  soils  is  in  the  form  of  grains  of  quartz 
more  or  less  modified.  This  form  of  silica  is 
probably  chemically  inert  in  regard  to  plant  growth 
but  it  plays  a  very  important  part  in  the  physical 
structure  of  soils  in  its  relations  to  plant  nutri- 
tion. 

Carbon  as  an  elementary  substance  occurs  as 
diamond  and  graphite  and  in  an  impure  form  as 
anthracite  and  bituminous  coals.  In  peat  and 
mucks  carbon  is  the  chief  constituent.  This  sub- 
stance is  also  contained  in  the  organic  matters  of 
the  soil  known  as  humus,  and  the  relation  of  the 
carbon  to  nitrogen  often  throws  important  light 
upon  the  amount  and  character  of  the  nitrogenous 
matters.  The  humus  content  of  the  soil  also 
affects  its  relation  to  water  and  to  the  absorption, 


20       MANUFACTURE  OF  FERTILIZING  MATERIALS 

retention  and  radiation  of  heat.  In  combination 
with  oxygen  it  forms  the  chief  food  of  growing 
plants,  the  carbon  of  the  carbon  dioxide  of  the 
air  being  elaborated  into  the  tissue  of  the  plants 
and  the  oxygen  returned  to  the  atmosphere. 
The  content  of  carbon  dioxide  in  the  air  is  from 
three  to  five  parts  per  10,000  by  volume.  As  a 
constituent  of  carbonates  this  element  helps  to 
form  some  of  the  most  important  ingredients  of 
the  earth's  crust,  namely,  limestone,  marbles, 
dolomites,  etc.,  and,  as  a  result  of  organic  activity, 
it  is  found  in  the  shells  of  the  crustaceans.  The 
calcareous  matters  of  the  soil,  that  is,  the  car- 
bonates of  lime  therein  found,  are  of  the  highest 
importance  from  an  agricultural  point  of  view. 
They  not  only  favor  the  process  of  converting 
nitrogenous  bodies  into  forms  suitable  for  plant 
food,  but  also  exert  a  most  potent  influence  on  the 
physical  state  of  the  soil  and  its  capacity  for  hold- 
ing water  and  permitting  its  flow  to  the  rootlets  of 
the  plant. 

Sulphur  occurs  in  nature  in  both  the  free  and 
combined  state.  In  the  free  state  it  is  found  in 
volcanic  regions  such  as  Sicily,  Iceland  and  the 
Western  United  States.  Its  usual  form  of  occur- 
rence is  in  combination  with  the  metals  to  form 
sulphides,  or  with  oxygen  and  a  metal  to  form  sul- 
phates. Sulphur  and  iron  combine  to  form  iron 
pyrites  or  iron  disulphide  (FeS2),  while  sulphur, 
oxygen,  and  calcium  are  found  in  gypsum,  an 
important  fertilizing  material. 


ORIGIN  AND  COMPOSITION  OF  SOILS          21 

Sulphur  plays  an  important  part  in  the  nour- 
ishment of  plants,  being  found  in  them  both  as 
sulphuric  acid  and  in  organic  compounds;  it 
is  an  essential  constituent  of  both  animal  and 
vegetable  protein  and  is  thus  intimately  associated 
with  one  of  the  most  important  classes  of  foods. 

Hydrogen  is  a  colorless,  invisible  gas,  without 
taste  or  smell.  It  occurs  free  in  small  propor- 
tions in  certain  volcanic  gases,  and  in  natural 
gas,  but  its  most  common  form  is  in  combination 
with  oxygen  as  water  (H^O),  of  which  it  forms 
11.19  per  cent  by  weight.  It  also  occurs  in  com- 
bination with  carbon  to  form  the  hydrocarbons, 
such  as  the  mineral  oils  (petroleum,  etc.),  and 
gases.  Hydrogen  is  of  no  importance  to  agri- 
culture in  a  free  state,  but  water  is  the  most 
important  and  necessary  of  all  plant  foods. 

Chlorine  occurs  free  in  nature  only  in  limited 
amounts  in  volcanic  vents.  Its  most  common 
form  is  in  combination  with  hydrogen,  forming 
hydrochloric  acid,  or  with  the  metals  to  form 
chlorides.  It  combines  with  sodium  to  form 
sodium  chloride  or  common  salt  (NaCl),  which 
is  the  most  abundant  mineral  ingredient  in  sea 
\vater  and  which  can  usually  be  detected  in  rain 
and  ordinary  terrestrial  waters.  In  this  form, 
also,  it  exists  as  extensive  beds  of  rock  salt,  which 
is  mined  for  commercial  purposes. 

Chlorine  is  found  uniformly  in  plants  and  may 
be  regarded  as  a  common  constituent  thereof. 
Common  salt  applied  to  a  soil  modifies  its  power 


22      MANUFACTURE  OF  FERTILIZING  MATERIALS 

of  attracting  and  holding  water.  Its  further 
action  has  already  been  explained. 

Phosphorus  never  occurs  in  nature  in  a  free 
state  but  exists  in  combination  in  greater  or  less 
quantities  in  all  soils  and  in  many  minerals.  Its 
combinations  are  also  found  in  large  deposits  of 
mineral  known  as  phosphorite,  apatite  and  as  so- 
called  pebble  and  phosphate  rock.  Phosphorus 
in  some  sort  of  combination  is  one  of  the  most 
essential  elements  in  animal  and  plant  food. 
In  animals  its  compounds  form  almost  all  of 
the  mineral  matter  of  the  bones,  and  in  plants 
they  are  important  constituents  of  the  ash  of 
seeds.  It  exists  in  organic  combination  both  in 
animal  and  vegetable  tissue  as  lecithines  and 
other  compounds. 

Nitrogen  as  a  mineral  constituent  of  soils,  is 
found  chiefly  in  the  form  of  nitrates,  but  owing  to 
their  solubility,  they  cannot  accumulate  in  soils 
exposed  to  heavy  rainfalls.  The  gaseous  nitrogen 
in  the  soil  is  also  of  some  importance,  since  it  is 
on  this  material  that  the  organisms  which  have  a 
symbiotic  activity  with  the  rootlets  of  some  plants 
probably  act  in  the  process  of  the  fixation  of 
atmospheric  nitrogen  in  a  form  accessible  to  plants. 
Nitrogen  in  the  free  state,  it  is  believed,  is  not 
directly  absorbed  into  the  tissues  of  green  plants. 
It  is  necessary  that  it  be  oxidized  in  some  way  to 
nitric  acid  or  some  compound  containing  it  before 
it  can  be  assimilated.  The  importance  of  nitro- 
gen as  a  plant  food  has  been  already  described. 


ORIGIN  AND  COMPOSITION  OF  SOILS          23 

Boron  occurs  chiefly  in  volcanic  regions,  but  is 
much  more  widely  distributed  in  the  soil  than  was 
formerly  believed.  It  is  a  constituent  of  the  ash 
of  many  plants,  and  is  thought  by  some  to  be  a 
true  plant  food.  A  more  reasonable  theory  is 
that  its  presence  in  vegetable  products  is  a  mere 
incident  to  its  occurrence  in  the  soil.  It  is  one  of 
the  least  abundant  of  the  elements,  not  occurring 
in  sufficient  quantity  to  find  a  place  in  our  inves- 
tigation. Boric  acid  and  borax  are  used  to  some 
extent  as  a  preservative. 

Fluorine  does  not  occur  free  in  nature,  but  it 
exists  chiefly  in  combination  with  calcium,  form- 
ing fluorspar,  traces  of  which  are  found  widely 
distributed.  In  combination  chiefly  with  lime 
it  occurs  in  bone  and  many  other  substances. 
It  is  one  of  the  elements  which  does  not  combine 
with  oxygen,  and  can  be  isolated  only  with  the 
greatest  difficulty.  At  most,  very  small  traces  of 
it  are  found  in  soils.  Fluoride  of  lime  is  found, 
however,  in  considerable  quantities  in  certain 
phosphate  deposits. 

Aluminum  is,  probably,  next  to  oxygen  and 
silicon,  the  most  abundant  element  of  the  earth's 
crust,  of  which  it  is  estimated  to  form  about  one- 
twelfth.  It  has  never  been  found,  in  nature,  in 
the  free  state,  but  commonly  occurs  in  combina- 
tion with  silicon  and  oxygen,  in  which  it  is  an 
abundant  constituent  of  feldspar,  mica,  kaolin, 
clay,  slate,  and  many  other  rocks  and  minerals. 

By  the  weathering  of  feldspar,  mica,  and  other 


24       MANUFACTURE  OF  FERTILIZING  MATERIALS 

minerals  containing  aluminum,  true  clay  is  formed, 
which  is  of  the  greatest  importance  in  the  con- 
stitution of  the  soil.  The  compounds  of  aluminum 
are  not  important  as  plant  food  except  when  they 
contain  potash  but  they  form  valuable  constituents 
of  the  soils,  furnishing  a  large  part  of  its  bulk,  and 
modifying  in  the  most  profound  degree  its  physical 
properties.  It  is  the  custom  of  some  to  use  the 
word  clay  to  designate  the  fine  particles  of  soil 
which  have,  in  general,  the  same  relations  to 
moisture  and  tilth  as  the  particles  of  weathered 
feldspar,  etc.  In  a  strict  chemical  sense,  however, 
the  term  clay  is  applied  only  to  the  silicates  of 
alumina  and  the  silica  found  therewith  formed. 
The  fertility  of  a  soil  is  indirectly  dependent  on 
the  quantity  of  clay  which  it  contains,  its  relations 
to  moisture  and  amenability  to  culture  being 
largely  conditioned  upon  its  clay  content.  The 
determination  of  the  percentage  of  clay  in  soils 
is  an  operation  of  the  highest  utility  in  forming  an 
opinion  of  the  value  of  a  soil  based  on  physical 
data  alone. 

Calcium  is  one  of  the  commonest  and  most 
important  elements  of  the  earth's  crust,  of  which 
it  has  been  estimated  to  compose  about  one- 
sixteenth.  It  does  not  occur  free  in  nature,  but 
its  most  common  condition  is  in  combination  with 
carbon  dioxide,  forming  the  mineral  calcite, 
marble,  and  the  very  abundant  limestone  rocks. 
In  this  form  it  is  slightly  soluble  in  water, 
especially  when  containing  carbon  dioxide,  and 


ORIGIN  AND  COMPOSITION  OF  SOILS          25 

hence  lime  is  very  generally  found  in  natural 
waters,  in  which  it  constitutes  the  chief  ingredient 
necessary  for  the  formation  of  the  shells  and  skele- 
tons of  the  various  species  of  mollusca  and  corals. 
In  combination  with  sulphuric  acid  calcium  forms 
the  rock  gypsum  and  other  forms.  Lime  is  not 
only  a  necessary  plant  food,  but  also  influences  in 
a  marked  degree  the  physical  condition  of  the 
soil  and  the  progress  of  nitrification.  Many 
clay  soils  are  rendered  porous  and  pulverulent  by 
an  application  of  lime,  and  thus  made  far  more 
productive.  The  sourness  or  acidity  of  soils  is 
also  corrected  by  the  application  of  lime.  Although 
existing  in  great  abundance,  it  has  not  com- 
manded the  degree  of  attention  from  agricultural- 
ists which  its  merits  deserve.  It  forms  an  essen- 
tial ingredient  of  plants  and  animals,  in  the  latter 
being  collected  chiefly  in  the  bones,  while  in 
plants  it  is  rather  uniformly  distributed  through- 
out all  the  tissues.  Both  in  common  language  and 
in  chemistry  the  term  lime  is  applied  to  the 
product  of  burning  limestone  (carbonate  of  lime) 
until  the  carbon  dioxide  is  expelled.  In  the  freshly 
burned  state,  lime  contains  no  water.  When  ex- 
posed to  the  air  it  gradually  absorbs  water  and 
carbon  dioxide,  which  enter  into  chemical  combi- 
nation, forming  air-slaked  lime.  Lime  is  changed 
into  slaked  lime  with  great  rapidity  and  with  the 
evolution  of  much  heat  on  the  application  of  water. 
Magnesium  occurs  chiefly  in  combination  with 
silica  and  carbon  dioxide  or  with  lime  and  carbon 


26      MANUFACTURE  OF  FERTILIZING  MATERIALS 

dioxide  in  the  mineral  dolomite.  It  is  intimately 
associated  with  calcium  and  a  trace  of  it  is  nearly 
always  found  where  lime  occurs  in  any  consider- 
able quantity.  The  bitter  taste  of  sea  water  and 
some  mineral  waters  is  often  due  to  the  presence 
of  salts  of  magnesia.  In  combination  with  silica 
it  forms  an  essential  part  of  such  rocks  as  serpen- 
tine, soapstone,  and  talc.  Magnesia  is  useful, 
especially  in  the  formation  of  seeds,  but  it  is  not 
absent  from  other  parts  of  the  plant.  It  performs 
its  functions  best  in  the  presence  of  calcium  com- 
pounds and  in  the  absence  of  the  latter  magnesia 
salts  may  easily  be  injurious. 

Potassium  combined  with  silica  is  an  important 
element  in  many  silicates  as,  for  instance,  ortho- 
clase,  Granite  rocks  usually  contain  consider- 
able quantities  of  potassium,  and  on  their  decom- 
position this  becomes  available  for  plant  food. 
In  the  form  of  chloride,  potassium  is  found  in 
small  quantities  in  sea  water,  and  as  a  nitrate  it 
forms  the  valuable  salt  known  as  niter  or  salt- 
peter. Potassium,  as  is  the  case  with  phosphorus, 
is  universally  distributed  in  soils,  and  forms  one 
of  the  great  essential  elements  of  plant  food. 
Under  the  form  of  kainite  and  other  minerals 
large  quantities  of  potassium  are  used  for  fertiliz- 
ing and  for  the  manufacture  of  pure  salts  for  com- 
mercial and  pharmaceutical  purposes.  The  or- 
dinary potassium  salts  are  very  soluble  and  for 
this  reason  they  cannot  accumulate  in  large  quan- 
tities in  soils  exposed  to  heavy  rainfall.  In  the 


ORIGIN  AND  COMPOSITION  OF  SOILS          27 

form  of  carbonate,  potassium  forms  one  of  the 
chief  ingredients  of  hard-wood  ashes,  and  in  this 
form  of  combination  is  especially  valuable  for 
fertilizing  purposes ;  potash  salts,  being  extremely 
soluble,  are  likely  to  be  held  long  in  solution. 
Some  of  them  are  recovered  in  animal  and  vege- 
table life,  but  the  great  mass  of  potash  carried 
into  the  sea  still  remains  unaccounted  for.  The 
recovery  of  waste  of  potash  is  chiefly  secured  by 
the  isolation  of  sea  waters  containing  large  quan- 
tities of  this  salt  and  their  subsequent  evapora- 
tion. Such  isolation  of  sea  waters  takes  place  by 
means  of  geological  changes  in  the  level  of  the  land 
and  sea.  In  the  raising  of  an  area  above  the 
water  level,  there  is  almost  certain  to  be  an 
enclosure,  of  greater  or  less  extent,  of  the  sea 
water  in  the  form  of  a  lake.  This  enclosure  may 
be  complete  or  only  partial,  the  enclosed  water 
area  being  still  in  communication  with  the  main 
body  of  the  sea  by  means  of  small  estuaries.  If 
this  body  of  water  be  exposed  to  rapid  evapora- 
tion as  was  doubtless  the  case  in  past  geological 
ages,  there  will  be  a  continual  influx  of  that 
evaporated.  The  waters  may  thus  become  more 
and  more  charged  with  saline  constituents.  Finally 
a  point  is  reached  in  the  evaporation  when  the 
less  soluble  of  the  saline  constituents  begin  to  be 
deposited.  In  this  way  the  various  formations 
of  mineral  deposits,  produced  by  the  drying  up  of 
enclosed  waters  takes  place. 

Sodium  is  never  found  free  in  nature,  but  its 


28       MANUFACTURE  OF  FERTILIZING  MATERIALS 

most  common  form  is  in  combination  with  chlorine 
as  common  salt,  an  important  ingredient  of  sea 
water.  Combined  with  silica  sodium  is  an  im- 
portant element  in  many  silicates.  Sodium,  al- 
though closely  related  to  potassium  chemically, 
cannot  in  any  case  be  substituted  therefor  in 
plant  nutrition.  While  it  is  certain  that  plants 
can  thrive  without  a  trace  of  sodium,  it  is  believed 
to  be  helpful  in  some  cases,  and  its  salts  may 
replace  those  of  potassium  in  so  far  as  osmotic 
and  neutralizing  functions  are  concerned.  In 
combination  with  nitrogen  it  forms  soda  (or  Chile) 
saltpeter  which  is  a  valuable  fertilizer  on  account 
of  its  content  of  nitric  acid. 

Iron  is  the  most  abundant  of  the  heavy  metals, 
and  occurs  in  nature  both  free  and  combined  with 
other  elements.  In  the  free  state  it  is  found 
only  to  a  limited  extent  in  basaltic  rocks  and 
meteorites,  but  in  combination  with  oxygen  it  is 
one  of  the  most  widely  diffused  of  metals,  and 
forms  the  coloring  matter  of  a  large  number  of 
rocks  and  minerals.  In  this  form,  too,  it  exists  as 
the  valuable  ores  of  iron  known  as  magnetite  and 
hematite.  In  combination  with  sulphur  it  forms 
the  mineral  pyrite,  Fe$2.  The  yellow  and  red 
colors  of  soils  are  due  chiefly  to  iron  oxides.  Iron 
salts  are  essential  to  the  production  of  chloro- 
phyll, the  coloring  matter  in  leaves,  and  to  its 
functional  activity.  Iron  is  one  of  the  essential 
constituents  of  the  haemoglobin,  or  red  coloring 
matter  therein,  without  which  oxygen  could  not 


ORIGIN   AND  COMPOSITION  OF  SOILS          29 

be  properly  carried  to  every  part  of  the  animal 
body. 

Titanium  is  apparently  of  no  importance  in 
plant  nutrition,  but  its  occurrence  in  many  soils 
requires  notice.  It  has  been  found  to  be  one  of 
the  most  widely  distributed  elements. 

Manganese,  next  to  iron,  is  the  most  abundant 
of  the  heavy  metals.  It  occurs  in  nature  in  com- 
bination with  oxygen,  in  which  form  it  is  associ- 
ated in  minute  quantities  with  iron  in  igneous 
rocks  or  in  the  forms  known  mineralogically  as 
pyrolusite,  psilomelane  and  wad.  As  the  peroxide 
of  manganese  it  occurs  in  concretionary  forms 
scattered  abundantly  over  the  bottom  of  the  deep 
sea.  It  is  found  in  the  ash  of  some  plants,  but  is 
not  believed  to  be  essential  to  plant  growth. 

Chromium  in  so  far  as  known  takes  no  part  in 
plant  nutrition  and  its  occurrence  in  the  soil  is 
only  of  importance  from  an  analytical  and  color 
standpoint. 

Barium  occurs  in  nature  combined  with  sul- 
phuric acid,  forming  the  mineral  barite,  or  heavy 
spar,  or  with  carbon  dioxide  forming  the  mineral 
witherite.  It  is  of  small  importance  from  an 
agricultural  standpoint. 


CHAPTER   III 

THE  RELATION  BETWEEN  SOILS  AND 
FERTILIZING  MATERIALS 

Exhaustible  Elements  and  '  Non-exhaustible  Elements — 
Preference  Shown  by  Plant  Life — Separate  Fertilizing 
Ingredients — Economy  in  Separate  Ingredients. 

A  MANURE  is  a  substance  designed  to  supply  one 
or  more  of  the  essential  constituents  of  plant  food, 
and,  where  necessary,  to  improve  the  physical 
condition  of  the  soil  to  which  it  is  applied.  The 
essential  constituents  of  plant  food  must  contain 
the  elements  carbon,  hydrogen,  oxygen,  nitrogen, 
phosphorus,  sulphur,  potash,  lime,  magnesia,  and 
iron  and  probably  silicon,  chlorine  and  sodium. 
Of  these,  carbon,  hydrogen  and  oxygen,  and  some 
of  the  nitrogen  are  derived  from  air  and  rain, 
most  of  the  nitrogen  and  the  remaining  elements 
being  obtained  from  the  soil.  Almost  every  soil 
contains  enough  Ca,  Mg,  S,  Fe,  Si,  Cl,  and  Na 
for  the  growth  of  a  full  crop,  but  nitrogen,  phos- 
phorus and  potash  are  often  present  in  but  small 
quantity,  and  become  exhausted  by  the  removal 
of  farm  produce. 

A  general  manure  or  fertilizer  is  usually  under- 
stood to  be  the  agency  which  can  supply  these 
three  constituents,  but  inasmuch  as  some  crops 

30 


SOILS  AND  FERTILIZING   MATERIALS  31 

either  contain  an  excess  of  one  or  other  of  these, 
or  are  better  able  to  obtain  some  one  or  other  of 
them  from  the  soil,  than  are  other  crops,  it  is 
frequently  economical  to  apply  a  special  manure 
to  meet  the  needs  of  such  crops.  For  what  is 
known  as  to  the  requirements  of  individual  crops 
a  work  on  agricultural  chemistry  must  be  con- 
sulted. It  thus  happens  that  special  manures 
are  divided  into  phosphatic,  nitrogenous,  and 
potash  manures.  It  is  necessary,  in  order  for  a 
manure  to  be  efficient,  that  it  shall  not  only  con- 
tain the  requisite  constituent  or  constituents  of 
plant  food,  but  that  the  nutriment  shall  be  in  an 
assimilable  form,  and  it  has  been  ascertained  that 
in  whatever  condition  the  plant  food  may  be 
actually  absorbed,  the  absorption  occurs  the  more 
rapidly  the  more  soluble  the  food  constituents  of 
the  fertilizer. 

There  is  no  way  to  tell,  without  experiment, 
what  food  constituents  a  soil  lacks.  The  crops 
themselves  give  valuable  suggestions.  As  a  rule 
lack  of  nitrogen  is  indicated  when  plants  are  pale 
green  in  color,  or  when  there  is  small  growth  of 
leaf  or  stalk,  other  conditions  being  favorable.  A 
bright,  deep  green  color,  with  a  vigorous  growth  of 
leaf  or  stalk,  is,  in  case  of  most  crops,  a  sign  that 
nitrogen  is  not  lacking,  but  does  not  necessarily 
indicate  that  more  nitrogen  could  not  be  used  to 
advantage.  An  excessive  growth  of  leaf  or  stalk, 
accompanied  by  an  imperfect  bud,  flower,  and  fruit 
development,  indicates  too  much  nitrogen  for  the 


32       MANUFACTURE  OF  FERTILIZING  MATERIALS 

potash  and  phosphoric  acid  present.  When  such 
crops  as  corn,  cabbage,  grass,  potatoes,  etc.,  have 
a  luxuriant,  healthful  growth,  an  abundance  of 
potash  in  the  soil  is  indicated;  also  when  fleshy 
fruits  of  fine  flavor  and  texture  can  be  successfully 
grown.  On  the  contrary,  when  these  plants  fail 
or  a  luxuriant  growth,  or  are  very  low  grade  in 
quality,  it  is  certain  indication  that  potash  is 
lacking.  When  a  soil  produces  good,  early  matur- 
ing crops  of  grains  with  plump  and  heavy  kernels, 
phosphoric  acid  will  not  generally  be  found 
deficient  in  the  soil. 

In  order  to  ascertain  with  greater  certainty 
what  food  elements  are  lacking  in  the  soil,  care- 
ful experiments  would  have  to  be  carried  out  on 
the  soil  and  crops,  by  applying  different  kinds 
of  fertilizing  materials  in  different  combinations, 
using,  for  example,  potash  compounds  in  one  com- 
bination, phosphoric  acid  compounds  in  another, 
nitrogenous  materials  in  another.  Then  different 
combinations  can  be  made  on  other  portions  of  the 
crop.  Some  portions  of  the  field  can  be  left  with- 
out application  of  any  kind.  The  result  can  then 
be  studied  in  the  yield  of  crop.  In  carrying  on 
such  field  tests,  several  difficulties  may  be  met. 
The  season  may  frequently  be  such  as  to  interfere 
seriously  with  the  favorable  action  of  the  fertilizing 
materials  applied.  Thus,  a  severe  drought  may 
counteract  all  other  conditions  and  prevent  a 
satisfactory  yield.  The  difference  of  mechanical 
condition  of  the  soil  on  the  same  farm  or  even  in 


SOILS  AND  FERTILIZING  MATERIALS          33 

the  same  field  may  prevent  a  fair  comparison  of 
the  action  of  different  kinds  of  fertilizing  materials 
and  elements.  But,  notwithstanding  such  diffi- 
culties, valuable  suggestions  will  be  gained  from 
an  experimental  study  of  the  soil  through  the 
behavior  of  the  crops. 

It  is  a  fact  of  great  interest  and  importance  that 
one  form  of  a  fertilizing  constituent  is  preferred 
by  some  plants  to  the  same  constituent  in  another 
form.  This  perference  is  indicated  by  greater 
yield  or  better  quality  of  product  or  by  both. 
Thus,  wheat  seems  to  give  better  results  when 
nitrogen  is  applied  in  the  form  of  nitrate  of  soda 
than  in  any  other  form.  The  quality  of  tobacco 
is  injured  by  potash  in  the  form  of  muriate  and, 
hence,  only  sulphate  of  potash  should  be  used 
for  fertilizing  purposes.  The  quality  of  sugar 
beets  and  of  potatoes  appears  to  be  better  when 
sulphate  of  potash  is  used. 

While  the  soil  may  contain  quantities  of  fer- 
tilizer naturally,  in  most  cases  it  will  not  pay  to 
give  serious  attention  to  this  source  of  fertiliza- 
tion. Nitrate  of  soda,  when  used  alone  should 
always  be  applied  to  growing  crops,  and  for  quick 
effects.  For  young  fruit  trees  or  for  vegetables, 
one  or  more  applications  may  be  made  with  bene- 
fit. Complete  fertilizers  usually  have  a  small 
proportion  of  their  nitrogen  in  the  form  of  nitrate 
of  soda,  and  the  remainder  in  a  less  active  form, 
so  that  by  the  time  the  nitrate  of  soda  is  utilized, 
the  nitrogenous  products  become  effective. 


34       MANUFACTURE  OF  FERTILIZING  MATERIALS 

Sulphate  of  ammonia  is  a  quick-acting  nitro- 
genous fertilizer,  but  should  be  used  only  when  the 
soil  has  been  lately  limed.  All  forms  of  potash 
are  equally  available,  but  should  be  applied  as 
early  in  the  season  as  possible;  even  fall  applica- 
tions are  advisable,  as  there  is  little  danger  of  loss 
through  drainage.  Lime  also  aids  the  effective- 
ness of  potash  salts.  Phosphates  in  the  form  of 
superphosphate  or  acid  phosphates  are  very 
quickly  available,  resembling  nitrate  of  soda  in 
this  respect,  though  it  is  hardly  advisable  to  make 
more  than  one  application,  early  in  the  season  or 
at  planting  time.  All  other  forms  of  phosphates 
are  best  applied  in  the  fall,  or  very  early  in  the 
spring. 

It  will  generally  be  found  more  economical  to 
purchase  fertilizing  materials  of  high  grade.  In 
applying  fertilizers,  bulk  is  often  desirable,  but  in 
purchasing  commercial  fertilizers,  the  object  should 
be  to  secure  as  much  nitrogen,  potash  and  phos- 
phoric acid  in  available  form  as  possible,  for  one 
dollar,  instead  of  as  many  pounds  as  possible  of 
fertilizers,  regardless  of  the  amount  of  plant  food 
contained  in  it.  This  is  particularly  applicable 
to  mixed  fertilizers.  Since  there  is  a  smaller 
bulk  to  handle  in  mixing,  a  smaller  number  of 
packages  for  holding  and,  consequently,  less 
weight  and  freight,  it  is,  as  a  rule,  more  economical 
to  purchase  fertilizers  in  their  more  concentrated 
forms.  For  illustration,  it  is  more  economical  to 
purchase  one  ton  of  high-grade  fertilizer  than 


SOILS  AND  FERTILIZING  MATERIALS          35 

three  tons  of  a  low-grade  fertilizer,  one  ton  of 
the  former  containing  the  same  amount  of  plant 
food  contained  in  three  tons  of  the  latter;  be- 
cause, in  making  the  latter,  three  times  as  many 
packages  or  bags  are  required  and  three  times  as 
much  freight  must  be  paid  all  for  the  same  amount 
of  plant  food. 

Fertilizers  cannot,  as  a  rule,  be  in  too  finely 
powdered  condition  nor  can  they  be  too  dry. 
With  many  materials,  bone,  for  example,  the 
availability  as  plant  food  is  directly  dependent 
upon  the  fineness  of  division.  Excessive  moisture 
in  fertilizer  is  undesirable  on  several  grounds. 
First,  the  larger  the  amount  of  moisture,  the 
smaller  will  be  the  amount  of  plant  food  in  a  ton. 
Second,  excess  of  moisture  causes  the  particles 
to  stick  together,  and  is  likely  to  result  in  caking 
and  clogging  when  used  in  drills.  Third,  an  excess 
of  moisture  favors  the  decomposition  and  loss  of 
nitrogen  in  many  forms  of  organic  matter.  This 
is  shown  by  the  fact  that  some  fertilizers  give  off 
a  very  offensive  odor  if  allowed  to  become  damp, 
while  they  are  comparatively  free  from  disagree- 
able odors  if  they  are  thoroughly  dry.  A  strong 
odor  in  a  fertilizer  is  an  indication  that  organic 
matter  is  decomposing  and  nitrogen  is  being  lost. 

Materials  which  are  readily  soluble  can  be  scat- 
tered over  the  surface.  After  the  first  rainfall 
they  distribute  themselves  throughout  the  soil 
very  completely  and  uniformly.  Such  materials 
are  nitrate  of  soda,  sulphate  of  ammonia,  soluble 


36       MANUFACTURE  OF  FERTILIZING  MATERIALS 

phosphates  and  soluble  potash  salts.  Fertilizers 
which  dissolve  easily  and  diffuse  through  the  soil 
rapidly  and  which  are  not  readily  retained  by  the 
soil,  are  best  applied  only  when  the  crops  are 
ready  to  utilize  them.  If  put  on  too  early,  there 
is  danger  of  their  leaching  from  the  soil  and  being 
carried  away  beyond  the  reach  of  the  plant,  and 
thus  lost.  Hence,  it  is  not  wise  ordinarily  to 
apply  guano,  ammonia  compounds  or  nitrate  of 
soda  in  the  fall,  except  in  climates  which  have  a 
dry  fall  and  winter.  Their  application  should  be 
deferred  until  spring.  In  wet  springs,  ammonia 
compounds  are  preferably  applied  rather  than 
nitrate  of  soda;  or,  if  nitrate  of  soda  is  used,  loss 
may  be  avoided  by  making  several  small  applica- 
tions instead  of  one  at  the  start. 

In  applying  highly  concentrated  commercial 
fertilizers,  it  is  wise  to  prevent  the  fertilizer  coin- 
ing in  contact  with  the  seeds  or  foliage  of  plants. 
Fertilizers  containing  ammonia  compounds  should 
not  be  mixed  with  wood  ashes,  lime,  or  Thomas 
slag  (odorless  phosphate),  since  some  of  the 
ammonia  is  likely  to  be  lost. 


CHAPTER  IV 

PEBBLE  PHOSPHATE  ORE  DRESSING  AND 
MILLING 

Steam  Shovels  and  Hydraulic  Mining  Practice 

FLORIDA  phosphates,  classed  as  hard  rock,  soft 
rock,  land  pebble,  and  river  pebble,  are  found  in 
the  Eocene,  Miocene,  and  more  recent  geolcgical 
formations.  The  hard-rock  phosphates  occur 
massive,  laminated,  and  as  boulders  piled  together, 
also  in  the  form  of  pebbles  where  the  other  rocks 
have  been  broken  by  weathering  and  water  move- 
ments. This  kind  of  material  possesses  a  variable 
structure  from  compact  to  fibrous,  and  while 
usually  of  a  creamy  color  is  frequently  stained 
with  iron  oxide. 

The  soft  rock  occurs  in  deposits  by  itself  and 
associated  with  hard  rock  phosphate.  It  may  be 
clayey  or  sandy  and  fill  spaces  between  boulders  of 
hard  rock  phosphate.  It  is  evidently  a  secondary 
deposit  formed  by  the  disintegration  of  other  phos- 
phates of  lime. 

It  carries  from  20  to  30  per  cent  less  phosphate 
of  lime  than  hard  rock  phosphate,  which  varies 
from  80  to  85  per  cent. 

Land-pebble  phosphate  is  essentially  a  mass  of 
whitish  phosphate  pebbles  varying  in  size  from 

37 


38      MANUFACTURE  OF  FERTILIZING  MATERIALS 

grains  to  1  in.  in  diameter,  averaging  possibly  a 
little  over  J  in.  They  are  hard  and  have  usually 
a  matrix  of  phosphate  clay  and  sand.  The  per- 
centage of  phosphate  of  lime  which  the  pebbles 
contain  is  from  75  to  80,  but  the  average  material 
as  mined  would  not  reach  this  standard.  This  ore 
is  mined  open  cut,  by  dredging,  and  by  hydraul- 
icking;  it  is  then  washed,  dried,  and  shipped  to 
fertilizer  works,  mostly  abroad. 

River-pebble  phosphates  are  found  as  bars  in 
the  rivers  of  southern  Florida,  and  with  them  are 
found  the  fossil  remains  of  vertebrates.  The 
river  pebble  is  blue  or  black,  varying  from  1  in. 
downward  in  size,  and  frequently  occurring  as  the 
hardened  casts  of  small  molluscs.  The  percentage 
of  phosphate  of  lime  in  the  river  pebbles  is  between 
58  and  68;  at  present  river  dredging  for  phos- 
phate pebbles  is  not  as  active  as  the  mining  opera- 
tions for  land  pebbles. 

Florida  phosphate  beds  are  covered  with  soil  to 
varying  depths,  which  is  removed  by  means  of 
steam  shovels  or  hydraulic  nozzles.  If  the  deposits 
are  below  water  level,  traction  dredges  working  on 
the  land,  or  floating  dredges,  are  used. 

The  overburden  of  land  deposits  is  stripped 
from  the  ore  by  steam  shovels,  a  cut  being  taken 
the  full  swing  of  the  shovel  boom,  and  the  shovel 
moved  forward  a  short  rail  length  when  this  is 
finished. 

The  capacity  of  the  dipper  or  shovel  varies  from 
1  to  2 1  cu.yd.,  and  the  boom  and  dipper  arm  is 


PEBBLE  PHOSPHATE  ORE  DRESSING          39 

made  to  conform  to  the  depth  of  the  alluvions. 
For  example,  a  35-ft.  boom  will  raise  material 
18  to  20  ft.  above  the  shovel  track  and  make  a 
cut  35  ft.  wide.  The  cars  to  carry  the  overburden 
are  standard  gauge  of  12  cu.yd.  capacity.  They 
are  usually  dumped  by  hand,  although  some  of  the 
more  recent  cars  have  air-dumping  arrangements 
which  are  controlled  from  the  engine  cab.  The 
cars  are  run  out  to  .the  dump  and  handled  in  the 
usual  manner,  care  being  taken  not  to  waste  the 
material  where  it  will  cover  future  work.  Steam 
shovel  work  is  done  by  contract,  the  price  being 
20  cents  per  cu.yd. 

Whenever  conditions  are  favorable  and  space 
available  for  the  disposal  of  the  material,  the 
overburden  is  removed  by  the  hydraulic  method, 
and  pumped  into  an  abandoned  excavation  from 
which  the  phosphate  ore  has  been  removed.  The 
cost  of  stripping  by  the  hydraulic  method  is  from 
5  to  8  cents  per  cu.yd.  The  overburden  in  Florida 
phosphate  fields  is  favorable  for  this  kind  of  work, 
being  clean,  fine  sand,  with  some  pebbles,  the 
majority  of  the  foreign  substances  being  sods, 
stumps  and  palmetto  roots.  Occasionally  the 
sand  is  cemented  and  grades  into  a  soft,  but  tough, 
sandstone  which  must  be  blasted  before  hydraulick- 
ing.  Owing  to  the  overburden  containing  little 
clay,  it  can  be  stacked  in  large  dumps  that  do  not 
liquefy  and  run  into  the  streams. 

In  Florida  where  hydraulic  stripping  is  prac- 
ticed, hydraulic  mining  may  be  also,  in  which  case 


40       MANUFACTURE  OF  FERTILIZING  MATERIALS 

the  material  is  broken  by  playing  one  or  more 
streams  of  water  under  a  pressure  of  from  90  to 
140  Ib.  per  sq.in.  against  the  face  of  the  deposit. 
This  operation  causes  the  rock  containing  the 
phosphate  to  crumble  and  flow  into  a  ditch  cut 
in  the  underlying  marl.  The  flow  is  aided  at 
times  by  additional  water  from  a  J-in.  nozzle 
ditch  hose,  the  object  being  to  drive  the  material 
into  a  sump  about  8  ft.  square  cut  in  the  marl. 
From  the  sump  the  material  is  lifted  by  an  8-in. 
or  10-in.  centrifugal  pump  and  discharged  into 
the  washers.  Since  the  rock  material  consists  of 
firm  sand  and  round  phosphate  pebbles,  very 
little  of  it  being  over  1 J  in.  in  diameter,  it  is  easily 
made  to  flow  through  the  ditch  into  the  sump,  on 
a  grade  of  2  in.  to  the  foot,  by  the  use  of  about 
ten  times  its  weight  of  water. 

The  hydraulic  nozzles  are  connected  to  the  main 
water  supply  pipe  which  is  usually  10  in.  in  diam- 
eter. Where  two  nozzles  are  worked  each  has 
from  200  to  500  ft.  of  6-in  diameter,  flanged, 
spiral-riveted,  galvanized  water  pipe.  Asphalt 
roofing  paper  or  tar  board  is  used  for  flange  gas- 
kets. At  one  or  two  convenient  places,  in  this 
6-in.  line,  a  ball-and-socket  joint  is  applied  to 
facilitate  the  lateral  movements  of  the  nozzles. 

When  two  nozzles  are  used  they  are  pointed  so 
as  to  wash  the  material  to  a  central  point,  which 
is  the  ditch  leading  to  the  sump.  In  case  the 
ditch  clogs,  an  auxiliary  hose  is  coupled  just  back 
of  the  nozzles  and  the  flow  of  water  from  this  is 


PEBBLE   PHOSPHATE  ORE   DRESSING  41 

used  to  move  the  material  to  the  sump.  After 
the  face  of  the  rock  is  mined  so  far  away  from  the 
sump  that  the  material  does  not  flow  properly 
through  the  ditch,  a  new  sump  is  blasted  50  to  75 
ft.  nearer  the  working  face,  and  the  pump  is 
moved  to  it.  The  pressure  required  for  hydraulic 
mining  of  this  kind  is  not  high,  but  the  work 
demands  a  large  volume  of  water  in  order  to  trans- 
fer the  material  through  the  ditch  to  the  sump  and 
not  choke  the  pump  by  an  excess  of  solids. 

The  outfit  for  transferring  the  ore  to  the  washer 
consists  of  a  centrifugal  pump  of  the  volute  box 
type,  with  chilled  cast-iron  facing,  directly  con- 
nected to  the  slip-ring  motor.  The  tail-piece  of 
the  pump,  which  must  be  flexible,  is  raised  from 
the  sump  by  means  of  a  set  of  triple  blocks  sus- 
pended from  a  tripod.  This  arrangement  is  nec- 
essary, because  whenever  the  mouth  of  the  suc- 
tion pipe  becomes  clogged  with  grass,  roots,  etc., 
it  must  be  raised  out  of  the  water  for  cleaning. 
In  case  the  distance  is  more  than  800  to  900  ft. 
between  the  mine  pump  and  washer,  a  relay  pump 
is  usually  installed.  In  such  cases  the  mine  pump 
discharges  into  a  sump  from  which  the  relay  pump 
draws  its  material  and  forces  it  to  the  washer. 
This  method  is  used  owing  to  the  difficulty  arising 
from  back  flow  and  water  hammer  when  operating 
two  centrifugal  pumps  in  series.  Where  the 
centrifugal  pump  discharges  without  much  head, 
the  end  of  the  pipe  line  is  elevated  for  a  pipe 
length  at  an  angle  of  45°  in  order  to  furnish  suf- 


42       MANUFACTURE  OF  FERTILIZING  MATERIALS 

ficient  pressure  head  to  work  against  and  prevent 
vibrations  in  the  pump. 

After  the  material  reaches  the  washer  from  the 
mines  it  is  delivered  to  a  relay  pump  without  going 
into  a  sump.  This  pump  lifts  the  material  to 
the  top  of  the  washer,  where  it  is  discharged  into  a 
launder  that  feeds  a  rotary  screen  having  IJ-in. 
holes.  The  screen  makes  two  products;  an  over- 
size consisting  of  mud  balls  and  coarse  rock 
which  is  sent  directly  to  the  tailing  pond,  and  an 
undersize  which  is  discharged  on  to  an  inclined 
stationary  screen  with  A-in.  slop  openings,  where 
some  of  the  sand  is  removed,  the  operation  being 
assisted  by  sprays  of  water.  The  oversize  from 
this  screen  passes  to  a  16-ft.  double  log  washer 
which  discharges  the  material  into  another  16-ft. 
single  log  washer.  These  logs  separate  the  par- 
ticles of  phosphate,  sand,  and  pebble  from  the 
silica  by  reason  of  their  grinding  and  mixing  action. 
Wash  water  is  also  supplied  to  the  logs,  which 
assists  the  separation  by  moving  the  silica  sand 
backwards  and  over  the  tail-gate  of  the  log-box. 
The  last  set  of  logs  discharges  on  to  a  shaking 
screen  which  further  eliminates  all  but  about  6 
to  8  per  cent  of  the  remaining  silica  and  the  greater 
part  of  the  water.  The  dewatered  material  from 
this  screen  goes  directly  into  a  hopper-bottom 
storage  bin  over  the  railroad  tracks,  where  it  is 
ready  for  transportation. 


CHAPTER  V 

HARD   ROCK  PHOSPHATE   ORE   DRESSING   AND 
MILLING 

Loss  of  Soft  Ores — Separating  the  Ores  from  Clays,  etc., 
and  Process  of  Roasting  or  Drying 

THAT  there  is  considerable  loss  of  phosphate  in 
mining  is  well  known.  Practically  all  the  deposits 
contain,  with  other  material,  more  or  less  phos- 
phate in  a  soft  or  pulverulent  condition.  Under 
present  methods  of  mining  and  treatment  this 
"soft"  phosphate  is  necessarily  lost  in  the  proc- 
ess of  washing,  being  carried  to  the  dump  along 
with  the  sand,  clay,  and  other  constituents  of  the 
matrix.  The  amount  of  phosphate  thus  discarded 
may  be  expected  to  vary  with  different  deposits 
and  under  different  conditions.  After  reaching 
the  dump  there  is  more  or  less  mechanical  separa- 
tion so  that  samples  taken  from  one  part  of  the 
dump  may  be  found  richer  in  phosphate  than 
from  some  other  part  of  the  same  dump.  Samples 
taken  at  random  by  the  writer  and  analyzed, 
from  some  phosphate  dumps  in  the  hard  rock 
region  gave  the  following  analyses:  Total  phos- 
phoric acid,  9.99  to  12.14;  which  is  equivalent 
to  tricalcium  phosphate,  21.81  to  26.50.  In  an- 

43 


44       MANUFACTURE  OF  FERTILIZING  MATERIALS 


HARD  ROCK  PHOSPHATE  ORE  DRESSING      45 

other  case,  a  sample  of  floats  from  the  dumps  in  the 
land  pebble  section  gave  as  follows:  total  phos- 
phoric acid,  11.47;  equivalent  to  tricalcium  phos- 
phate, 25.04.  In  still  another  analysis  made  of  the 
plate-phosphate  ore,  it  was  as  follows:  silica, 
58.95  to  60.10;  iron  and  alumina,  11.70  to  11.20; 
calcium  phosphate  26.80  to  27.92.  It  is  estimated 
in  this  particular  case  that  approximately  four  tons 
of  material  was  excavated  and  washed  in  order  to 
obtain  one  ton  of  the  high  grade  rock  phosphate 
(77  per  cent).  From  this  it  is  evident  that  of  the 
material  taken  from  the  pit  three-fourths,  carry- 
ing about  27  per  cent  calcium  phosphate,  goes  to 
the  dump,  while  one-fourth,  carrying  77  per  cent 
calcium  phosphate,  is  saved;  thus  of  the  total 
phosphate  ore  taken  from  the  pit,  in  this  instance 
at  least,  one-half  goes  into  the  dump. 

From  these  data  it  is  apparent  that  a  large 
amount  of  phosphate  ore  is  being  lost  annually  in 
this  section  and  that  any  economical  method  of  re- 
claiming this  waste  or  of  utilizing  the  floats,  if  such 
be  devised,  are  clearly  of  the  greatest  importance 
to  the  phosphate  industry,  and  ultimately  to  the 
agricultural  interests  of  the  whole  country. 

With  the  extension  of  agriculture  necessary  to 
support  increased  population,  together  with  the 
progressive  exhaustion  of  the  new  and  naturally 
rich  soils,  there  arise  increased  demands  upon  the 
phosphate  supply.  At  the  present  this  demand  is 
coming  mostly  from  the  older  countries  of  Europe, 
and  the  phosphate  now  produced  is  largely  ex- 


46       MANUFACTURE  OF  FERTILIZING  MATERIALS 

ported.  The  time  is  not  far  distant,  however,  when 
an  equally  strong  demand  will  come  from  the  ex- 
hausted soils  of  our  own  country.  The  hydraulic 
and  steam-shovel  methods  of  stripping  the  over- 
burden and  the  mining  of  rock,  to  a  certain  extent, 
is  described  in  Chapter  I  of  this  work.  In  the 
pits  in  the  hard  rock  section,  steam  dipper  dredges 
are  used,  which  load  the  skips  that  are  hauled  up  an 
incline  and  delivered  to  the  top  of  the  washer. 
The  phosphate  ore  thus  carried  from  the  pits  is 
dumped  upon  "  grizzlies, "  where  it  is  sized.  That 
which  passes  through  the  bars  of  the  "grizzlies" 
is  ready  for  sizing  by  the  "  separator, "  or  trommel, 
but  that  which  is  too  large  to  pass  through  the  bars 
is  broken  by  hand  with  a  pick,  axe  or  dynamite 
and  made  ready  to  pass  through  the  bars  of  the 
grizzly.  The  ore  passing  into  the  "separator" 
is  sized  for  the  first  time  for  the  set  of  double 
log  washers  where  it  receives  its  first  treatment 
for  the  removal  of  the  clay  which  adheres  to 
the  phosphate  material.  That  part  of  the  ore 
which  is  too  large  to  pass  through  the  per- 
forations of  the  revolving  screen,  passes  out 
the  lower  end  and  falls  into  a  roll-jaw  crusher 
and  after  being  crushed  it  falls  through  a  chute 
into  the  first  set  of  log  washers  where  it  is 
washed  with  ore  which  has  been  sized  by  the  re- 
volving screen  or  trommel.  In  the  log  washer,  one 
end  of  the  washer  revolves  in  a  gudgeon  placed 
below  the  water  in  the  box  containing  the  ore  to  be 
washed;  the  other  end  works  in  journals.  The 


HARD  ROCK  PHOSPHATE  ORE   DRESSING      47 

log,  which  is  driven  by  gear-wheels,  works  the  ore 
towards  the  head  of  the  box  and  discharges  it  into 
the  second  washer  which  is  a  single  log.  Water 
is  introduced  at  the  upper  end  of  the  box,  while  the 
ore  is  fed  at  the  lower  end;  the  clean  water  thus 
meets  the  ore  and  when  it  becomes  dirty  it  flows 
out  at  the  lower  end,  carrying  with  it  the  clay  in 
suspension.  There  is  no  general  standard  for  these 
log  washers.  The  box  is  about  four  feet  deep  at 
one  end  and  two  feet  at  the  other,  according  to  the 
length  of  the  logs,  which  vary  from  sixteen  feet 
to  thirty  feet  and  are  pitched  at  an  angle  sufficient 
to  give  a  rise  of  one  and  one-quarter  inches  to  the 
foot.  The  dirty  water  from  the  washers  generally 
flows  away  in  sluices,  but  where  the  fall  is  not 
sufficient  a  centrifugal  pump  of  some  type  is  used 
to  assist  in  its  removal. 

After  the  log  washers  have  removed  most  of  the 
clayey  matter,  the  ore  passes  through  a  chute  into 
a  trommel  with  an  internal  spray,  which  eliminates 
the  remaining  clay  and  the  smaller  portions  of  the 
sand  from  the  ore.  These  screens  have  jackets 
ranging  from  one-eighth  inch  to  one-sixteenth  inch, 
and  are  commonly  known  as  "rinsers. "  The  ore 
after  passing  through  the  "rinser, "  falls  through  a 
chute  on  to  a  slowly  revolving  table,  known  as  a 
"  picking-table, "  where  boys  and  old  men  pick  out 
the  "sand  rock"  and  other  foreign  matter  not  re- 
moved by  the  log  washers  and  screens.  The  ore 
after  hand-sorting  is  automatically  pushed  through 
the  center  of  the  table  by  a  large  brush  or  scraper 


48       MANUFACTURE  OF  FERTILIZING  MATERIALS 


into  a  chute  leading  to  a  car  under  the  picking- 
table,  in  which  it  is  carried  to  the  drying  shed, 


where  it  is  kiln-dried  before  being  loaded  into  the 
railway  box  cars  for  transportation. 


HARD  ROCK  PHOSPHATE  ORE  DRESSING      49 


FIG.  2a. — Hard  Rock  Phosphate  Mill 


DETAILED   DESCRIPTION   OF   FIG.   2a 

No.  1,  incline  track  running  from  the  phosphate  pits  up  the 
top  of  the  washer  upon  which  the  crude  ore  is  hauled  in  the 
skip-cars. 

No.  2,  skip-car  delivering  a  load  of  phosphate  ore  to  the 
grizzle  bars. 

No.  3,  pulley  or  sheave  at  the  top  of  washer  upon  which  runs 
the  wire  cable  that  hauls  the  skip-car  up  the  incline  track. 

No.  4,  grizzle  bars  upon  which  the  ore  is  dumped  and  where 
it  receives  its  first  sizing,  and  is  forced  through  and  broken 
up  before  falling  into  the  separator. 

No.  5,  chute  from  bars  to  separator. 

No.  6,  separator  which  sizes  the  rock  for  the  first  set  of  double 
log  washers.  That  which  passes  out  of  the  separator  falls  in. 


50     MANUFACTURE  OF  FERTILIZING  MATERIALS 

the  crusher,  and  is  crushed  for  the  log  washer  when  too  large 
to  pass  through  the  separator. 

No.  7,  crusher  which  crushes  the  rock  for  the  log  washers. 

No.  8,  first  set  of  double  log  washers. 

No.  9,  set  of  single  log  washers  where  the  rock  goes  after 
passing  through  the  set  of  double  log  washers. 

No.  10,  rinser  which  gives  the  rock  its  final  washing  before 
depositing  upon  the  picking  tables  where  it  is  picked  by  hand. 

No.  11,  circular  picking  table  upon  which  the  rock  is  picked. 

No.  12,  ore  bin  where  rock  is  dumped  after  being  picked 
on  picking  table. 

No.  13,  mine  car  that  receives  ore  from  the  bottom  of  the 
ore  bin  through  a  chute,  and  is  used  to  carry  the  ore  to  the 
drying  sheds,  where  it  is  burnt  before  loading  upon  the  railroad 
cars  for  transportation. 

No.  14,  200  H.P.  engine  horizontal  type,  for  driving  ma- 
chinery. 

Nos.  15  and  16,  line  shafts  for  pulleys  and  belting. 

No.  17,  hoisting  drum  for  hoisting  skip-cars  from  pits  up 
to  the  washer  to  dump  the  wet,  crude  ore  on  bars  for  treatment. 

No.  18,  universal  joint  connecting  shafts  of  log  and  line 
shafts  as  all  log  washers  have  to  be  inclined  to  allow  water  to 
run  down  through  them  to  thoroughly  wash  ore. 

Nos.  19  and  20,  other  universal  joints  in  shafting. 

No.  21,  chute  for  sliding  ore  into  separator. 

No.  22,  gearing  of  the  log  washers. 

To  reduce  the  moisture  to  the  required  3  per  cent 
the  producers  of  land-pebble  phosphates  use  me- 
chanical dryers  entirely.  While  there  are  several 
kinds  of  these  dryers,  all  are  of  the  rotary-cylinder 
type;  that  is,  heated  air  and  gases  of  combustion 
are  made  to  pass  through  the  cylinder  from  a 
furnace.  The  wet  phosphate  ore  is  fed  automat- 
ically into  the  cylinder  and  by  means  of  shelving 


HARD  ROCK  PHOSPHATE  ORE  DRESSING      51 

riveted  to  the  sides  of  the  cylinder  is  gradually 
worked  from  the  cold  to  the  hot  end,  being  repeat- 
edly showered  through  the  hot  gases  in  its  passage 
until  discharged.  The  fuel  is  coal,  wood,  or  crude 
petroleum. 

The  excess  of  moisture  in  the  hard  rock  in  this 
section  of  Florida  during  the  early  years  of  mining 
was  removed  entirely  by  kiln  burning,  a  process 
still  in  use  by  many  operators.  For  this  purpose 
the  phosphate  ore  is  placed  on  ricks  of  wood. 
The  wood  is  then  fired,  and  the  phosphates  partly 
smothering  the  flames  permits  slow  burning,  and 
by  the  gradual  spread  of  heat,  the  phosphate  be- 
comes more  or  less  uniformly  dried.  More  re- 
cently, with  the  growing  scarcity  of  wood  in  the 
hard-rock  section  several  large  producers  have 
installed  mechanical  dryers  similar  to  those  used 
by  the  land-pebble  miners.  In  a  number  of  in- 
stances the  mechanical  dryers  are  in  different  parts 
of  the  country,  and  away  from  the  actual  mining 
operations. 


CHAPTER  VI 
PHOSPHORUS 

Origin  of  Phosphate  Rock,  Basic  Slag,  Bone  Meal,  Ammonium 
Sulphate,  Sodium  Nitrate,  Organic  Nitrogenous  Materi- 
als, Potash  and  Guano. 

IT  is  a  well-known  fact  that  phosphorus  is  an 
element  and  like  the  element  iron,  is  almost  uni- 
versally distributed  over  the  globe,  and  is  found 
in  all  living  things.  Therefore,  it  is  reasoned  that 
it  may  like  iron,  be  accumulated  in  large  beds 
by  natural  law  which  governs  the  concentration 
of  mineral  masses.  Again  it  is  suggested  that 
phosphoric  acid,  derived  from  mollusca,  deposits 
from  birds,  fish  and  saurians,  has  filtered  down  and 
replaced  the  carbonic  acid  in  the  underlying  lime- 
stone, converting  it  into  phosphate  of  lime.  It  is 
true  that  in  many  instances  the  phosphate  of  lime 
very  rarely  contains  any  trace  of  organic  remains, 
while  the  limestone  on  which  it  rests  abounds  in  the 
casts  of  mollusca  in  some  sections  of  the  Southern 
States.  Then  again,  in  proximity  to  the  hard  rock 
phosphate  is  a  soft  phosphate  of  lime  that  has  the 
consistency  of  soft  plastic  clay.  This  soft  phos- 
phate often  underlies  the  hard  rock  and  is  several 
feet  in  thickenss.  This  condition  prevails  in  the 
hard  rock  phosphate  section  of  Florida. 

52 


PHOSPHORUS 


53 


Speaking  of  phosphates  in  general,  however,  the 
fact  has  been  noted  that  within  the  rain  belt,  when 


bfl 

C 

I 

CO 

I 


guano  deposits  rest  upon  limestone  the  phosphoric 
acid  is  leached  out  and  transforms  the  carbonate  of 


54       MANUFACTURE  OF  FERTILIZING  MATERIALS 

lime  to  phosphate  of  lime.  An  instance  of  this  is 
cited  in  which  limestone  in  one  of  the  South  Pacific 
islands  was  believed  to  have  been  changed  to 
phosphate  to  a  depth  of  several  feet  within  a 
period  of  twenty  years.  The  phosphoric  acid  in 
this  instance  was  leached  by  rainwater  from  re- 
cently deposited  guano.  The  belief  has  been  ex- 
pressed that  the  phosphoric  acid  of  the  phosphates 
has  been  derived  directly  from  bird  guano.  The 
local  character  of  the  bird  rookeries  determines 
the  local  occurrence  of  phosphate  rock. 

Whether  the  hard  rock  phosphates  of  Florida 
resulted  from  a  superficial  and  heavy  deposit  of 
soluble  guano,  or  from  the  concentration  of  phos- 
phate of  lime  already  widely  and  uniformly  dis- 
tributed throughout  the  mass  of  original  rock,  or 
from  both  of  these  sources  is  regarded  as  a  difficult 
question.  The  writer  does  not  believe,  however, 
that  the  bird-guano  theory  will  account  for  these 
widely  disseminated  phosphates  any  better  than 
for  the  intensely  localized  hard  rock  phosphates. 
The  key  to  the  solution  of  the  hard-rock  phosphate 
problems  is  found,  in  the  writer's  opinion,  in  a 
study  of  the  geological  history  of  each  particular 
section  of  the  world's  deposits. 

However,  the  evidence  of  the  formation  of  phos- 
phate by  the  transformation  of  carbonate  of  lime 
into  the  phosphate  of  lime  is  entirely  incontroverti- 
ble, since  many  of  the  boulders  retain  the  original 
calcareous  shells  now  phosphatized.  The  evidence 
of  subsequent  secondary  deposition  in  the  cavities 


PHOSPHORUS  55 

is  likewise  obtained  from  the  structure  of  the  rock 
itself.  This  condition  is  observed  in  the  hard-rock 
section  of  Florida. 

Basic  Slag. — It  has  been  found  within  recent 
years  that  the  phosphatic  slag  from  the  basic  proc- 
ess of  steel-making  possesses  considerable  value  as 
a  fertilizer.  The  content  of  phosphoric  acid  varies 
from  10  to  25  per  cent,  and,  according  to  some, 
the  phosphoric  acid  exists  as  calcium  phosphate. 
The  slag  is,  however,  of  little  value  as  a  manure 
unless  it  be  very  finely  ground — e.g.,  80  per  cent 
of  it  should  pass  a  sieve  having  100  meshes  per 
linear  inch.  The  attainment  of  this  condition  con- 
stitutes the  preparation  of  the  slag  for  the  market, 
and  is  expensive  on  account  of  hardness  of  the  ma- 
terial. Grinding  is  commonly  performed  by  a  ball 
mill  which  consists  essentially  of  a  drum,  the  inner 
surface  of  which  is  polygonal;  the  drum  contains 
a  number  of  cast-steel  balls  of  various  sizes.  Rota- 
tion of  the  drum  breaks  up  the  slag  by  the  rolling 
and  percussive  action  of  the  balls,  and  the  commi- 
nuted material  is  systematically  separated  by 
sieves  in  the  sides  of  the  drum.  The  sieves  which 
effect  the  final  separation  are  protected  from 
direct  contact  with  the  balls  by  perforated  iron 
plates. 

Bone  Meal. — This  is  of  manurial  value  on 
account  of  its  phosphates,  but  it  also  contains  ni- 
trogenous matter.  Fresh  bones  contain  about  f 
per  cent  of  nitrogen;  they  decompose  very  slowly 
when  used  as  a  manure.  When  the  bones  are 


56       MANUFACTURE  OF  FERTILIZING  MATERIALS 

previously  fermented  in  heaps,  the  nitrogenous 
matter  becomes  more  readily  assimilable. 

Bones  are  also  more  available  as  manure  when 
they  have  been  steamed  for  the  removal  of  fat. 
Boiled  bones  which  have  been  passed  through  the 
glue-maker's  hands  contain  a  smaller  proportion  of 
nitrogen  than  do  raw  bones.  The  boiled  bones 
can  be  more  finely  ground  and  divided  than  is 
represented  by  the  condition  of  bone  meal;  the 
fine  product  is  known  as  bone  flour.  Dissolved 
bones  is  the  product  of  the  treatment  of  bones  with 
commercial  sulphuric  acid. 

Ammonium  Sulphate. — This  is  produced  as  a 
by-product  in  the  destructive  distillation  of  coal. 
The  working  up  of  gas  liquor  for  ammonium 
sulphate  is  carried  out  in  the  following  manner: 
The  liquor  is  heated  to  drive  off  the  free  ammonia 
and  the  vapor  is  absorbed  in  sulphuric  acid,  form- 
ing ammonium  sulphate,  which  crystallizes  and  is 
periodically  fished  out.  It  is  the  common  practice 
in  some  countries  to  use  only  that  part  of  the  am- 
monia which  is  liberated  on  distilling  the  gas  liquor 
a" one,  but  sometimes  the  fixed  ammonia  is  liber- 
ated by  the  addition  of  lime.  Pure  ammonium 
sulphate  contains  21  per  cent  of  nitrogen,  corre- 
sponding to  25.75  per  cent  ammonia,  and  is  a  col- 
orless salt.  The  commercial  product  varies  in 
color  from  gray  to  brown,  owing  to  the  presence  of 
tarry  matter,  and  is  sometimes  yellowish  from  the 
presence  of  arsenic;  this  body  is  formed  by  the 
action  of  the  hydrogen  sulphide  from  the  gas  liquor 


PHOSPHORUS  57 

on  the  arsenic  present  in  the  sulphuric  acid  in 
which  the  ammonia  is  absorbed.  Commercial 
ammonium  sulphate  usually  contains  about  24.5 
per  cent  of  ammonia.  It  should  be  free  from  am- 
monium sulphocyanide,  which  is  a  plant  poison. 
This  impurity  is  rarely  present,  save  when  the  am- 
monium sulphate  has  been  made  by  the  direct  sat- 
uration of  gas  liquor  with  sulphuric  acid. 

Sodium  Nitrate. — Sodium  nitrate  is  obtained 
from  the  deposits  of  crude  nitrate  in  Chili 
and  Peru.  The  deposits,  which  lie  about  six  to 
ten  feet  below  the  surface,  are  known  as  caliche, 
and  form  a  layer  four  to  six  feet  deep.  It  is  asso- 
ciated with  clayey  substances;  the  composition  is, 
however,  very  various,  and  the  content  of  sodium 
nitrate  may  reach  50  per  cent. 

The  caliche  is  broken  in  a  stone  breaker,  and 
systematically  lixiviated  in  tanks  heated  by  closed 
steam.  Water  being  a  rare  commodity  in  nitrate 
districts,  it  has  to  be  used  for  repeated  extractions. 
When  the  liquid  reaches  a  specific  gravity  of  1.55, 
it  is  run  into  crystallizing  vats,  in  which  it  remains 
from  four  to  six  days;  the  mother  liquor  is  then 
run  off,  and  used  for  the  recovery  of  iodine. 
The  iodine  characteristically  present  in  crude  ni- 
trate probably  exists  as  iodate.  As  much  as  1  per 
cent  of  perchlorate  is  also  found  in  some  samples 
of  caliche,  and  lowers  the  value  of  the  latter  con- 
siderably, since  even  small  quantities  of  perchlorate 
are  injurious  to  plants.  The  nitrate  deposited 
after  having  been  sun-dried  has  the  following  com- 


58       MANUFACTURE  OF  FERTILIZING  MATERIALS 

position:  sodium  nitrate  96.75  per  cent;  sodium 
chloride  0.75  per  cent;  sodium  sulphate  0.30  per 
cent;  insoluble  matter  0.10  per  cent;  water  2.10 
per  cent. 

Organic  Nitrogenous  Materials. — Dried  blood 
obtained  from  slaughter-houses  is  a  type  of  these. 
It  contains  from  9  to  12  per  cent  nitrogen. 
Ground  hoofs  and  horns  form  another  manure 
of  this  class,  as  also  waste  woolen  material, 
such  as  shoddy  running  from  5  to  8  per  cent 
nitrogen. 

Potash. — Potash,  a  necessary  constituent  of 
plant  food,  has  been  supplied  mainly  as  one  or 
the  other  of  the  products  obtained  in  the  Stass- 
furt  mining  industry  of  Germany.  The  chief 
salts  are  kainit,  containing  12  to  14  per  cent  of 
potassium  oxide;  the  double  sulphate  of  potas- 
sium and  magnesium,  containing  27  to  28  per 
cent  potassium  oxide,  which  is  obtained  from 
kainit;  carnalite  with  about  11  per  cent  of  potas- 
sium oxide  in  the  crude  mineral;  and  crude 
potassium  chloride  of  a  strength  corresponding 
to  about  50  per  cent  potassium  oxide.  Magne- 
sium salts  and  chlorides  detract  to  some  extent 
from  the  manurial  value  of  these  substances. 

Guano.— This  is  the  excrement  of  sea  birds  in 
a  more  or  less  altered  condition.  A  distinction  is 
drawn  between  nitrogenous  and  phosphatic  gua- 
nos; the  former  are  either  of  recent  origin,  or  have 
not  been  subjected  to  weathering  which  is  the  case 
in  such  dry  climates  as  that  of  Peru;  the  latter 


PHOSPHORUS  59 

(found  in  Australasia)  have  been  so  washed  by 
rain  as  to  contain  little  or  no  nitrogen. 

Dry  Peruvian  guano  contains  its  nitrogen  in  the 
form  of  uric  acid  and  urates;  when  these  have 
undergone  partial  decomposition,  the  guano  be- 
comes damp  and  contains  ammonium  carbonate, 
to  fix  which  a  "  dissolved  "  guano  is  made  by  treat- 
ing with  sulphuric  acid,  the  ammonia  being  con- 
verted into  ammonium  sulphate  and  the  calcium 
phosphate  rendered  soluble.  An  "  equalized  " 
guano  is  a  Peruvian  guano  in  which  the  percentage 
of  ammonia  has  been  brought  up  by  suitable 
admixtures. 


CHAPTER  VII 
ARTIFICIAL   MANURE   MANUFACTURE 

Phosphatic  Manures — Mineral  Phosphates — Superphosphates 
— Precipitated  Phosphates — Mixed  Manures. 

THE  only  abundant  form  in  which  phosphorus  is 
found,  is  as  the  various  forms  of  calcium  phos- 
phate, and,  to  a  smaller  extent,  as  aluminium  and 
iron  phosphates.  Of  these,  the  calcium  phos- 
phates can  better  supply  phosphorus  to  the  plant 
than  can  iron  and  aluminium  phosphates,  prob- 
ably because  of  the  greater  ease  with  which  this 
compound  is  dissolved  by  feeble  acids,  e.g.,  car- 
bonic acid,  and  by  saline  solutions.  Deposits  of 
calcium  phosphate  are  widely  distributed.  The 
most  definite  mineral  containing  calcium  phos- 
phate is  apatite. 

Phosphates,  even  when  very  finely  ground,  are 
but  slowly  assimilated  by  plants,  and  are,  there- 
fore, almost  exclusively  used  for  making  super- 
phosphate, the  process  consisting  in  treating  them 
with  sulphuric  acid  in  order  to  realize  the  follow- 
ing equation 

Ca3(P04)2  +2H2SO4  =  2CaS04+CaH4(P04)2 

Superphosphate 

60 


ARTIFICIAL  MANURE  MANUFACTURE          61 


as  nearly  as  is  practicable,  CaH^PO^  being 
soluble  in  water.  Calcium  carbonate,  a  com- 
mon impurity  in  phosphates,  consumes  sulphuric 
acid  in  this  treatment.  Other  objectionable 
impurities  in  phosphates  are  the  ferric  oxide 
and  alumina,  because  both  oxides  form  in- 
soluble phosphates,  so  that  the  proportion  of  sol- 
uble phosphates  in  the  prepared  superphosphates 
is  diminished  by  their  presence.  Various  plans 
have  been  proposed  for  removing  calcium  carbon- 
ate —  e.g.,  treatment  with  an  aqueous  solution  of 
€62  or  S(>2  in  which  calcium  carbonate  is  soluble; 
or  by  causticising  the  lime  by  heat,  and  acting  upon 
it  with  ammonium  salt  —  e.g.,  the  chloride  —  the  am- 
monia being  recovered.  Redonda  phosphate  (es- 
sentially A1P04)  has  been  converted  into  an  avail- 
able form  by  treatment  with  sulphuric  acid, 
yielding  aluminium  sulphate  and  phosphoric  acid, 
or  by  heating  with  sodium  chloride  and  superheated 
steam,  whereby  a  portion  of  the  phosphoric  acid 
is  converted  into  sodium  phosphate. 

"Superphosphate"  is  a  mixture  of  calcium  sul- 
phate as  gypsum  with  the  acid  phosphate  of  lime 
CaH4(PO4)2  which  is  the  essential  manurial  con- 
stituent. The  crude  calcium  phosphate  to  be 
converted  into  superphosphate  should  be,  as 
stated  above,  as  free  as  possible  from  iron  and 
aluminium  compounds  (not  more  than  3  per  cent 
of  Fe2Os—  A^Os)  and  from  calcium  carbonate. 
The  material  is  ground  very  finely  —  e.g.,  to  pass 
a  sieve  having  80  meshes  per  linear  inch  —  and  is 


62       MANUFACTURE  OF  FERTILIZING  MATERIALS 

charged  intermittently  in  4  to  5  cwt.  lots  into  a 
mixer  composed  of  a  lead-lined  wooden  tank,  pro- 
vided with  an  agitator,  where  it  is  mixed  with 
chamber  acid  (vitriol  of  specific  gravity  1.53  to 
1.61,  containing  62.53  to  69.43  per  cent  H2S04), 
run  in  as  required  from  an  adjacent  tank.  The 
quantity  of  acid  needed  varies  with  the  composi- 
tion of  the  phosphate,  13  to  18  cwts.  per  ton  of 
phosphate  being  the  usual  limits.  The  mixer  is 
built  above  a  brick  chamber  known  as  the  "pit'7 
or  "den/7  and  into  this  the  semi-fluid  mass,  after 
it  has  been  agitated  for  a  few  minutes,  is  dis- 
charged through  a  chute.  The  temperature  of 
the  mass  in  the  pit  rapidly  rises  to  110°  C.  Much 
gas  is  evolved  (CCb,  HC1,  and  HF),  and  solidifi- 
cation sets  in.  The  gases  are  drawn  off  through 
flues,  and  pass  through  a  scrubber,  necessary  on 
account  of  the  objectionable  character  of  HC1, 
and  still  more  of  HF.  When  the  pit  is  nearly  full, 
one  of  the  sides,  which  is  of  wood  and  removable, 
is  taken  down  and  the  product  dug  out  and  passed 
through  a  disintegrator,  whereby  it  is  reduced  to 
powder.  When  mixed  manures  are  being  made, 
potash  salts  and  nitrogenous  materials  are  mixed 
during  passage  through  the  disintegrator. 

In  mixing  and  making  of  fertilizers,  it  was  first 
proposed  to  make  the  ingredients  correspond  to 
the  analysis  of  the  plant.  This  method  was  prac- 
ticed for  some  time,  biit  it  was  found  that  there 
was  already  in  the  soil  more  or  less  available  plant 
food  and  that  fertilizing  material  was  often  applied 


ARTIFICIAL   MANURE   MANUFACTURE          63 

where  one  or  more  constituents  could  be  omitted 
or  reduced  in  quantity.  It  was  then  suggested 
that  soil  analysis  should  form  the  basis  of  deter- 
mining the  needs  of  the  soil  for  different  crops,  but 
this  failed  to  produce  satisfactory  results.  The 
formulas  at  present  used  by  many  have  been  based, 
in  part,  upon  the  composition  of  the  plant,  and, 
in  part,  upon  actual  field  tests. 

The  amount  of  nitrogen  called  for  by  analysis 
of  plants  is  generally  reduced  because  we  can  de- 
pend upon  the  soil  to  furnish  a  considerable 
amount.  In  case  of  leguminous  crops,  the  amount 
of  nitrogen  which  we  need  to  supply  can  be  reduced 
to  a  small  fraction  of  what  the  plant  will  use, 
because  such  crops  can  draw  their  main  supply  of 
nitrogen  from  the  air. 

The  amount  of  soluble  phosphoric  acid  is  or- 
dinarily increased  above  what  plant  analysis  calls 
for,  because  the  solubility  is  more  or  less  de- 
creased after  the  fertilizer  comes  in  contact  with 
the  soil. 

The  proportion  of  sulphuric  acid  used  in  mak- 
ing a  superphosphate  is  generally  as  great  as  pos- 
sible without  impairing  the  dryness  of  the  finished 
manure.  It  is  usually  more  than  sufficient  for  the 
realization  of  the  equation  given  above.  It  is 
now  supposed  that  the  reaction  which  occurs  takes 
place  in  two  stages,  the  sulphuric  acid  first  liberat- 
ing an  equivalent  of  phosphoric  acid,  which  then 
reacts  with  the  remaining  CasffO^.  The  pres- 
ence of  calcium  sulphate  tends  to  solidify  the  mass 


64       MANUFACTURE  OF  FERTILIZING  MATERIALS 


by  combining  with  2  molecules  of  H2O  and  setting 
like  plaster  of  Paris. 


The  value  of  a  superphosphate  depends  on  its 
content  of  phosphoric  acid  soluble  in  water,  which 


ARTIFICIAL  MANURE   MANUFACTURE          65 

is  commercially  called  "soluble  phosphate'  '  —  i.e., 
the  amount  of  phosphoric  acid  found,  on  analysis, 
to  be  soluble,  is  calculated  back  to  Ca3(PO4)2. 
An  ordinary  superphosphate  will  contain  24  to 
30  per  cent  of  soluble  phosphate,  40  to  45  per  cent 
calcium  sulphate,  and  2  to  3  per  cent  of  insoluble 
phosphate.  Attempts  have  been  made  to  pro- 
duce superphosphate  containing  more  soluble  phos- 
phoric acid  than  the  quantity  mentioned  above, 
in  order  to  save  carriage;  thus  "double  super- 
phosphate "  is  made  by  extracting  an  ordinary 
superphosphate  with  water,  removing  the  calcium 
sulphate  by  means  of  a  filter  press,  and  evap- 
orating the  liquor  with  phosphate  that  has  already 
been  treated  with  a  quality  easily  attacked  by 
phosphoric  acid.  Such  preparations  may  contain 
80  to  90  per  cent  of  soluble  phosphate. 

When  superphosphate  is  kept,  a  portion  of  the 
soluble  phosphate  becomes  insoluble  in  water 
owing,  it  is  supposed,  to  the  interaction  of  calcium 
superphosphate  CaH4(PO4)2,  and  normal  calcium 
phosphate,  CasCPO^,  thus: 


CaH4(P04)2+Ca3(P04)2  =4CaHPO4. 

A  further  reaction,  which  has  been  already  men- 
tioned, occurs  between  the  ferric  oxide  and  alumina 
contained  in  crude  phosphate  and  a  portion  of 
the  phosphoric  acid,  insoluble  ferric  phosphate 
(FePO4)  and  aluminium  phosphate  (A1PO4)  being 
formed.  Although  such  "reverted  phosphate"  is 
insoluble  in  water,  it  is  more  soluble  in  saline  solu- 


66       MANUFACTURE  OF  FERTILIZING  MATERIALS 

tions — e.g.,  ammonium  citrate  solution — than  is  the 
natural  phosphate,  Cas(PO4)2,  and  is  reckoned  as 
possessing  a  certain  manurial  value.  These  points 
have  to  be  taken  into  consideration  in  the  analyti- 
cal examination  of  superphosphate. 

When  a  mineral  phosphate  will  not  pay  for  con- 
version into  superphosphate  it  may  be  used  for  the 
production  of  precipitated  phosphate,  which  con- 
sists mainly  of  "dicalcium  phosphate/ '  CaHP04. 
The  preparation  is  conducted  by  dissolving  the 
phosphate  in  hydrochloric  acid,  sufficiently  diluted 
to  leave  siliceous  matter  and  much  of  the  oxides 
of  iron  and  aluminium  undissolved.  The  solution 
is  neutralized  by  lime  or  chalk,  when  the  precipi- 
tated phosphate  is  thrown  down.  It  has  been 
proposed  to  utilize  waste  calcium  sulphide  for 
this  precipitation,  the  point  of  neutrality'  being 
discernible  by  the  formation  of  FeS;  the  EbS 
evolved  is  collected  for  use  as  a  source  of  sulphur. 
As  already  stated,  this  form  of  calcium  phosphate 
is  more  vluable  than  Ca3(P04)2,  and,  being  pre- 
cipitated, is  very  finely  divided;  it  contains  up  to 
40  per  cent  of  P20s,  and  is  much  used  abroad. 


CHAPTER  VIII 
MANUFACTURE   OF   SUPERPHOSPHATE 

THE  manufacture  of  superphosphate  comprises 
three  principal  operations:  1.  Grinding  the  raw  ma- 
terial. 2.  Rendering  the  ground  raw  phosphate 
soluble  by  sulphuric  acid.  3.  The  drying  of  the 
superphosphate. 

Raw  phosphate  should  be  carefully  ground,  be- 
cause it  is  found  that  the  fineness  of  the  phosphate 
contributes  to  a  great  extent  to  a  perfectly  suc- 
cessful superphosphate.  Thus  the  powder  should 
not  leave  more  than  10  per  cent  of  residue  on  a 
70  mesh  sieve,  and  this  residue  should  not  exceed 
the  size  of  groats;  it  is  only  at  this  cost  that  all  the 
phosphoric  acid  is  rendered  soluble.  Certain 
phosphates  are  delivered  ground,  others  in  lumps 
of  the  size  of  the  fist.  To  lend  itself  well  to  grind- 
ing the  phosphate  should  be  dry.  Florida  phos- 
phate especially  should  not  contain  more  than  1 
per  cent  of  moisture,  while  Algerian  phosphate 
grinds  very  well  with  5  per  cent  of  water.  When 
dealing  with  phosphate  drenched  with  sea  water 
in  transit  or  accidentally  in  the  warehouse  it  is 
extended  on  a  drying  platform  of  sheet  iron  heated 
by  the  combustion  gases  or  over  flues  from  the 
boiler  furnaces.  For  the  grinding  of  phosphate  at 

67 


68       MANUFACTURE  OF  FERTILIZING  MATERIALS 

the  present  day  ball  mills — continuously  fed 
and  discharged — are  in  general  use,  which  owing 
to  their  strong  construction  and  stable  working 
answer  well  for  the  purpose.  In  older  factories 
flatstone  mills  are  frequently  used.  Griffing  crusher 
with  a  walking  beam  has  likewise  some  rare  par- 
tisans, but  it  is  costly  and  requires  repairs  which 
become  heavy  in  the  end.  The  material  to  be 
introduced  into  this  grinding  machine  ought  pref- 
erably to  be  reduced,  and  for  that  purpose  edge 
runners  are  suitable.  The  crusher,  with  blades- 
disintegrator — is  likewise  used,  but  only  to  crush 
phosphate  in  large  pieces  or  rock  phosphate. 
These  machines  will  now  be  considered. 

Edge  runners  consist  generally  of  two  stones 
turning  on  a  circular  plate  round  a  vertical  shaft; 
at  the  same  time  each  stone  turns  round  its  own 
horizontal  axis,  and  grinds  the  material  both  by 
crushing  and  rubbing.  The  horizontal  axes  of  the 
two  mills  are  independent  of  one  another  and  each 
connected  with  the  vertical  shaft  by  means  of  a 
hinged  crank.  The  stones  can  thus  be  raised  or 
lowered  independently  of  each  other.  The  ma- 
terial is  fed  into  the  mill  directly,  by  shovel  or  by 
an  elevator;  it  is  drawn  continually  under  the 
stones  by  collectors,  and  when  it  is  sufficiently 
ground,  it  is  evacuated  by  the  automatic  discharge, 
sifted  and  bagged  up.  Two  men  are  sufficient  to 
attend  to  such  a  mill. 

Flatstone  mills  are  built  either  with  the  upper 
stone  stationary  or  the  lower  stone  stationary,  ac- 


MANUFACTURE  OF  SUPERPHOSPHATE    69 

cording  as  it  is  the  upper  or  lower  stone  that  is 
made  to  revolve.  Mills  of  the  first  kind  are  used 
for  crushing  very  hard  phosphate,  those  of  the 
second  kind  for  soft  phosphates.  The  foundation 
consists  of  cast-iron  columns  or  a  hollow  cast-iron 
support,  on  which  the  cage  of  the  mill  is  fitted  up. 
The  shaft  of  the  mill  is  sustained  by  a  movable 
bearing  with  collar;  its  lower  part  rests  in  a  socket. 
The  bearing  with  collar  is  screwed  to  the  bottom 
of  the  mill  cage  and  completely  protected  from 
dust.  The  adjustment  of  the  revolving  millstone 
is  done  by  means  of  an  endless  screw  or  by  lever 
transmission  with  screw,  and  hand  fly-wheel.  The 
number  of  revolutions  is  about  120  per  minute  for 
mills  five  feet  in  diameter,  under  which  conditions 
a  mill  can  grind  about  five  tons  of  phosphate  per 
hour  with  20  horse  power.  The  mill  is  fed  by  a 
cup  elevator  and  shaking  hopper;  a  single  workman 
with  an  assistant  can  attend  to  two  pairs  of  stones 
placed  side  by  side.  The  mills  of  the  same  group 
are  generally  driven  by  a  single  main  shaft  by 
direct  cog-wheel  gearing.  Generally  three  pairs 
of  stones  are  in  use,  two  of  which  are  at  work  and 
the  other  pair  being  faced.  A  great  many  other 
kinds  and  classes  of  mills  are  used  among  which  are 
the  ball  mills,  Pfeiffer's  Mill  with  combined  air 
separator,  which  is  a  kind  of  ball  mill,  and  the  jaw- 
breaker mill. 

The  phosphate  was  formerly  rendered  soluble 
in  pits  where  the  sulphuric  acid  and  phosphate 
were  hand-mixed  with  suitable  tools;  in  other 


70      MANUFACTURE  OF  FERTILIZING  MATERIALS 

words,  they  wrought  like  masons  making  mortar. 
But  for  thirty  years  this  work  has  been  done  ex- 
clusively by  mechanical  means,  which  enables  the 
work  to  be  done  more  rapidly  and  in  larger  quan- 
tities at  a  time. 

Consequently  the  mixing  pit  has  been  enlarged 
so  much  that  in  its  new  form  it  constitutes  the 
chamber,  or  more  familiarly  the  "den"  or  "house" 
in  which  the  phosphate  is  rendered  soluble.  This 
chamber  is  closed  and  care  has  to  be  taken  to  elim- 
inate and  render  inoffensive  the  toxic  gases  which 
are  disengaged  from  the  material  during  its  de- 
composition. 

To  mix  the  acid  with  the  phosphate  a  "mixer" 
or  mixing  machine  is  used,  constructed  and  in- 
stalled thus :  The  mixer  consists  of  an  egg-shaped 
pan  64  inches  wide  at  the  top  and  48  inches  wide 
at  the  bottom,  fitted  with  two  discharge  doors, 
with  lever  and  counterpoise,  which  enables  the 
mixing  to  be  run  into  an  enclosed  space,  called  the 
decomposition  chamber,  which  is  built  on  the 
ground  floor  or  sunk  in  the  ground.  In  the  pan  a 
vertical  shaft  turns,  driven  by  a  cog-wheel  gearing 
and  carrying  blades  of  a  special  form  arranged  in 
a  helicoid  manner;  these  lift,  throw  down,  and  trit- 
urate the  mass,  after  the  style  of  a  plough  as  it 
works  the  ground,  and  prevent  it  at  the  same  time 
from  being  deposited  and  attached  to  the  sides. 
It  suffices  to  pull  the  bent  levers  to  open  the  dis- 
charge doors,  and  thus  let  the  liquid  fall  into  the 
decomposition  chamber,  "den"  or  "house." 


MANUFACTURE  OF  SUPERPHOSPHATE    71 

The  pan  is  made  of  cast  iron,  with  2  per  cent  of 
a  special  alloy  which  renders  it  very  resistant  to 
acid.  The  arms  of  the  agitator  and  the  blades  as 
well  as  the  valves  are  of  cast  steel.  The  mixing 
shaft  makes  sixty  turns  a  minute;  the  mixing  is 
triturated  until  the  pulverized  phosphate  is  fine 
enough  to  pass  through  a  70-mesh  sieve.  As  the 
mixture  remains  longer  in  the  liquid  state,  the 
the  length  of  time  occupied  in  mixing  must  be  pro- 
longed. The  acid,  contained  in  a  lead-lined  tank, 
is  drawn  into  a  measuring  tank  by  turning  a  valve; 
it  then  flows  through  a  2-inch  lead  pipe  into  the 
mixer  in  the  form  of  a  fine  spray.  At  the  same  time 
the  crushed  phosphate — previously  weighed  and 
laid  on  sacks  on  two  inclined  planes  to  right  and 
to  left  of  the  mixer — is. run  into  the  mixer.  In 
certain  factories  the  phosphate  is  brought  to  the 
mixer  by  an  elevator,  and  received  in  buckets  by 
means  of  which  it  is  run  into  the  mixer.  The  bags 
retain  about  1  per  cent  of  phosphate  in  the  fabric. 
The  mixer  can  take  a  charge  of  about  495  to  550 
pounds.  When  the  phosphate  is  rich  in  carbonate 
of  lime  the  mixture  froths  and  threatens  to  prime. 
Such  a  mishap  is  obviated  by  diminishing  the 
amount  of  phosphate.  The  acid  and  phosphate 
ought  to  be  run  in  simultaneously  and  never  after 
each  other.  The  mixer  works  continuously  with  no 
stop  except  in  case  of  a  breakdown.  When  one 
mixing  is  finished  the  sides  of  the  mixer  are  rapidly 
dusted  with  a  little  phosphate  to  neutralize  any 
free  acid  left  there  which  might  corrode  the  metal. 


72       MANUFACTURE  OF  FERTILIZING  MATERIALS 


The  working  of  the  mixer  requires  three  men;  the 
first  takes  charge  of  the  machine,  the  second  SU- 


perintends  the  measuring  and  running  in  of  the 
acid,   the  third  brings  the  sacks  of  phosphate. 


MANUFACTURE  OF  SUPERPHOSPHATE    73 

The  charging  of  the  mixer  lasts  about  two  minutes; 
agitation  takes  two  minutes,  according  to  the  na- 
ture of  the  phosphate;  discharge  takes  half  a  min- 
ute. The  "den"  may  be  filled  to  three-fourths 
its  height;  the  vacant  space  serves  as  a  regulator 
for  the  evacuation  of  the  gas.  The  decomposi- 
tion of  the  phosphate  by  acid  is  effected  not  in  the 
mixer,  but  principally  in  the  "den"  or  "house." 
Cold  acid  is  used,  that  is,  acid  the  temperature  of 
which  varies  between  25  degrees  and  30  degrees  C. 
and  of  a  density  between  50  degrees  and  55  de- 
grees Be.  When  the  acid  is  at  a  lower  temperature 
the  mixing  does  not  heat  enough  to  drive  the  water 
off,  and  yield  a  dry  superphosphate.  When  the 
acid  is  too  hot  the  mixing  thickens  too  much  in  the 
mixer,  in  which  case  the  acid  may  be  further  di- 
luted. 

Owing  to  the  gas  given  off,  the  thick  liquid  effer- 
vesces, and  forms  air-bells  which  rise  to  the  sur- 
face; at  the  same  time  it  heats  up  to  248  to  302 
degrees  F.  Gradually  it  settles  in  the  "den"  and 
after  an  hour  it  sets.  An  addition  of  dolomite 
(carbonate  of  lime  plus  carbonate  of  magnesia) 
keeps  it  liquid  for  some  time  longer,  so  that  the 
water  evaporated  is  then  much  greater. 

All  the  heat  given  off  by  the  reaction  ought  to 
be  utilized  with  that  end  in  view,  that  is,  carrying 
off  the  water.  It  is  only  when  this  is  done  that 
perfect  solution  is  realized,  and  that  a  superphos- 
phate that  will  behave  well  on  subsequent  manipu- 
lations is  obtained.  Of  recent  years  attempts 


74      MANUFACTURE  OF  FERTILIZING  MATERIALS 

have  been  made  to  use  hot  sulphuric  acid  and  in- 
ject hot  air  into  the  chamber,  so  as  to  render  the 
phosphate  perfectly  soluble  and  to  start  the  drying 
of  the  superphosphate,  so  as  to  simplify  the  final 
operations.  But  the  results  obtained  were  not 
satisfactory.  The  opinion  of  certain  specialists 
may  be  endorsed.  Such  experiments  will  never 
be  successful,  because  it  is  irrational  to  exceed  a 
temperature  of  100  degrees  C.  in  the  "den"  except 
in  the  case  of  phosphate  of  a  very  good  quality  of 
which  there  is  no  need  to  fear  retrogradation.  It 
is  better  to  leave  the  substance  to  itself  during  its 
chemical  transformation  and  let  it  be  settled  by 
insensible  gradations.  Experiments  show,  more- 
over, that  the  injection  of  hot  air  into  the  mass 
gives  it  the  consistency  of  mastic,  which  the  manure 
manufacturer  always  tries  to  avoid,  knowing  full 
well  that  the  porosity  of  the  superphosphate  is  the 
best  condition  to  realize  for  subsequent  operations. 
The  construction  of  the  decomposition  house  is 
not  very  complicated.  The  walls  are  two-brick 
thick;  they  are  covered  inside  with  a  coating  which 
resists  acid.  To  consolidate  them  and  prevent 
them  yielding  under  the  pressure  of  the  mixing 
they  are  fortified  by  iron  T  pieces,  fixed  to  the 
base  by  masonry,  and  joined  to  the  roof  by  cramp- 
ing irons.  The  roof  consists  of  iron  T  pieces  three 
feet  apart,  laid  on  the  walls  and  connected  together 
by  iron  rods  or  arches  of  masonry,  the  whole  being 
covered  by  a  coat  of  cement.  All  the  ironwork  is 
covered  by  paint  to  resist  acid  fumes.  The  house 


MANUFACTURE  OF  SUPERPHOSPHATE    75 

is  fitted  with  solid  oak  or  pitch  pine  door  consoli- 
dated inside  by  planks  placed  crosswise  in  the 
gutters.  The  chinks  of  the  planks  and  the  doors 
are  luted  with  a  paste  of  clay  so  as  to  prevent  air 
penetrating. 

In  the  early  days  of  manure  manufacture  only 
one  "house"  was  used,  and  the  mixer  was  installed 
in  the  center  of  the  ceiling  of  the  house;  then  two 
houses  were  installed  with  the  mixer  stride-legs 
between  them;  finally,  later  on,  four  houses  have 
been  built  and  the  mixer  placed  at  the  crossing  of 
the  party  walls.  This  plan  gives  excellent  results. 
The  mixer  in  that  case  is  fitted  with  four  discharge 
doors  each  of  which  empties  into  a  house  of  its 
own.  Each  "den"  has  a  capacity  of  50  to  100 
tons  according  to  the  size  of  the  factory. 

Attempts  have  been  made  to  find  methods  of 
rendering  phosphate  soluble  more  rapidly  and  more 
completely  than  by  the  processes  actually  used. 
To  accomplish  this  the-phosphate  is  reduced  to  a 
very  fine  state  to  pass  through  a  No.  100  sieve. 
A  paste  is  made  of  it  by  drenching  it  with  water 
or  with  acid  of  10  to  20  degrees  Be.  and  finally 
adding  the  rest  of  the  acid  at  60  degrees  Be.  But 
this  process  was  soon  abandoned,  for  the  action 
was  too  violent  and  the  metal  of  the  mixer  was  at- 
tacked by  the  acid. 

Attempts  have  been  made  to  render  phosphate 
soluble  by  mixtures  of  hydrochloric  and  sulphuric 
acid  without  any  great  advantage.  The  super- 
phosphate contained  30  per  cent  of  hydrochloric 


76       MANUFACTURE  OF  FERTILIZING  MATERIALS 

acid,  which  rotted  the  bags,  besides  the  mixture  of 
sulphuric  acid  and  hydrochloric  acid  attacks  the 
metal. 

The  gases  formed  in  the  superphosphate  "dens" 
cannot  be  allowed  to  escape  into  the  atmosphere 
without  being  purified,  in  consequence  of  their  bad 
smell  and  corrosive  action.  They  are  generally 
passed  through  a  wash  tower  by  means  of  a  fan. 
The  fans  should  be  rather  powerful,  so  that  the 
amount  of  air  drawn  into  the  "den"  during  dis- 
charge is  sufficient  to  allow  the  laborers  to  empty 
the  "den"  under  good  conditions. 


CHAPTER   IX 
COMPOUND   MANURES 

THE  manures  generally  used  for  admixture  with 
superphosphates  are  Peruvian  guano,  bone  dust, 
sulphate  of  ammonia  and  nitrate  of  soda,  but  the 
Peruvian  guano  now  shipped  from  places  of  pro- 
duction is  much  less  rich  in  nitrogen  than  that  im- 
ported in  the  past.  Its  place  is  taken  by  sulphate 
of  ammonia,  ground  horn,  dried  blood,  dried  meat, 
etc.  Superphosphate  of  potash  is  also  prepared. 
The  mixing  is  done  as  much  as  possible  after  the 
phosphate  is  dissolved.  Mixing  is  not  done  in  the 
dry  state,  except  when  it  cannot  be  done  otherwise. 

Hand  labor  is  the  best  for  this  kind  of  work. 
The  materials,  previously  weighed  and  sifted,  are 
made  into  a  two-ton  heap  by  means  of  a  portable 
box  or  barrow  capable  of  holding  two  cwt.  To 
turn  the  matter  properly  the  shovel  is  plunged 
into  it  vertically,  so  as  to  mix  it,  then  after  having 
sifted  it,  it  is  made  into  a  heap  in  the  inverse  order, 
that  is  to  say,  by  lifting  it  from  the  ground  to 
throw  on  to  the  middle  of  the  heap. 

These  manipulations  are  sometimes  rather  un- 
pleasant, on  account  of  the  disengagement  of  dust, 
etc.,  nevertheless  they  form  the  best  method  of 
mixing.  The  materials  so  mixed  are  afterwards 

77 


78      MANUFACTURE  OF  FERTILIZING  MATERIALS 

passed  through  a  disintegrator  or  through  a  toothed 
crusher  and  a  very  homogeneous  mixture  is  thus 
obtained.  Inert  materials  should  be  avoided  in 
these  mixings.  By  mixing  high  strength  super- 
phosphate with  low  strength  superphosphate  com- 
mon kinds  can  be  made  without  recourse  to  inert 
materials,  such  as  sand,  plaster,  etc. 

Although  the  composition  of  ammoniated  su- 
perphosphate is  very  variable,  the  most  usual 
strength  being  9  X  9,  5  X 10  or  6  X 12,  the  first  figure 
indicating  the  percentage  of  nitrogen,  the  second 
the  percentage  of  soluble  phosphoric  acid,  this 
manure  is  in  great  esteem.  It  is  analogous  to  dis- 
solved Peruvian  guano  to  which  farmers  are  accus- 
tomed. It,  moreover,  presents  this  advantage, 
that  its  acid  retrogrades  less  easily  in  the  soil  than 
that  of  pure  superphosphate,  seeing  that  the  sul- 
phuric acid  combines  first  with  the  bases  which  it 
encounters  in  arable  land.  The  mixture  of  super- 
phosphate with  sulphate  of  ammonia  is  easily 
made.  Sulphate  of  ammonia  is  delivered  in  a 
finely  ground  granular  condition.  It  contains  24.5 
per  cent  NH3=20.2  per  cent  N  and  about  1  per 
cent  moisture,  which  is  an  advantage  for  the  man- 
ufacture, for  the  mixture  9x9  must  be  delivered 
with  a  miximum  of  6  to  7  per  cent  of  moisture, 
that  of  5x10  with  a  maximum  of  8  to  9  per  cent 
moisture,  if  it  is  desired  to  avoid  annoyances 
by  the  formation  of  lumps  or  loose  caking  in 
the  sacks.  To  obtain  very  homogeneous  super- 
phosphate of  ammonia,  the  sulphate  of  ammo- 


COMPOUND  MANURES  79 

nia  is  added  during  the  "dissolving"  of  the  super- 
phosphate by  dissolving  this  salt  in  the  sulphuric 
acid  used  to  decompose  the  superphosphate,  but 
this  method  of  proceeding  is  not  applicable  except 
with  small  amounts  of  sulphate  of  ammonia. 

The  process  generally  used  in  making  super- 
phosphate of  ammonia  is  as  follows:  The  dry 
superphosphate  of  ammonia  delivered  in  10-ton 
wagons,  being  stored  and  analyzed,  the  amount  of 
superphosphate  and  sulpnate  required  to  give  a 
mixture  of  9  X9  has  been  calculated.  Suppose  that 
the  sulphate  of  ammonia  contains  20.5  per  cent  N, 
then  20.5  kg.  correspond  to  100  kg.  (NH4)2SO4, 
9  kg.  correspond  therefore  to 


=42  kg.  (NH4)2S04. 


There  remains  then  for  the  superphosphate 
100  -42  =58  kg.  These  58  kg.  of  superphosphate 
must  contain  9  kg.  of  soluble  phosphoric  acid,  which 

100X9 
corresponds  to  -  =  15.5  per  cent  phosphoric 

Oo 

acid.  To  make  the  mixture  the  10  tons  of  sul- 
phate of  ammonia  are  laid  in  a  heap  33  feet  long 
and  on  each  heap  the  necessary  portion  of  super- 
phosphate to  the  total  12.77  tons.  Two  laborers 
mix  the  two  with  the  shovel,  making  the  whole  into 
one  heap  and  recommence  the  same  in  an  inverse 
direction.  The  mixer  is  then  passed  through  a  dis- 
integrator or  toothed  crusher,  then  it  is  laid  on  a 


80       MANUFACTURE  OF  FERTILIZING  MATERIALS 

big  heap  in  the  warehouse  for  the  ingredients  to 
combine. 

Mixtures  of  superphosphate  and  sulphate  of 
ammonia  exhibit  phenomena  of  a  peculiar  nature. 
They  gradually  heat  and  become  damp  to  the 
touch;  they  dry  again,  and  owing  to  the  forma- 
tion of  gypsum,  they  harden  more  and  more. 
The  reaction  lasts  for  a  variable  time.  It  depends 
on  the  nature  of  the  superphosphate  and  its  man- 
ner of  manufacture,  and  may  end  in  fifteen  days, 
when  the  mass  is  in  a  large  heap  and  exposed  to  a 
certain  pressure.  Superphosphate  of  ammonia 
forms  a  hard  rocky  mass,  the  shifting  of  which  is 
expensive,  for  one  is  obliged  to  blow  it  up  with 
gunpowder.  However,  only  neglect  of  the  man 
in  charge  of  the  mixer  in  not  running  in  the  proper 
amount  of  acid  would  produce  this.  It  is  then 
crushed  by  a  disintegrator,  is  passed  through  the 
sieve,  and  bagged  up  immediately  afterwards,  for 
it  does  not  solidify  again  if  made  according  to  rules, 
that  is  to  say,  if  each  grain  of  sulphate  of  ammonia 
is  united  to  its  grain  of  superphosphate  to  form  a 
sulphophosphate.  To  diminish  the  hardening  as 
much  as  possible,  sand  or  better  still  powdered 
peat,  sawdust,  wool  dust  or  chimney  soot  are 
added,  and  in  the  second  place,  immediate  satura- 
tion of  the  sulphate  of  lime  by  the  addition  of  a 
little  water.  The  second  grinding  is  therefore 
necessary  to  effect  the  perfect  mixing  of  the  two 
ingredients.  In  fact,  if  the  substance  be  analyzed 
after  the  first  crushing,  there  will  be  found  8.8 


COMPOUND   MANURES 


81 


82       MANUFACTURE  OF  FERTILIZING  MATERIALS 

per  cent  of  phosphoric  acid  and  9.2  per  cent  of 
nitrogen,  together  18  per  cent,  but  after  the  sec- 
ond crushing  the  product  uniformly  shows  9  per 
cent  of  phosphoric  acid  and  9  per  cent  of  nitro- 
gen. This  method  of  preparation  serves,  equally, 
for  all  the  mixing  if  desired  to  make  superphos- 
phate of  ammonia  5  XlO.  For  100  kg.  of  mixture, 

100  X5 

take =24.4  kg.   of  sulphate    of  ammonia 

^jU.o 

of  20.5  per  cent  N,  and  consequently  75.6  kg.  of 

100  X 10 

superphosphate  containing  -          -  =  13.2  per  cent 

75.6 

phosphoric  acid.  If  it  be  a  case  of  a  wagon  of 
10  tons  of  sulphate  of  ammonia,  41  tons  of  the 
mixture  will  be  obtained  of  the  5x10  mixture,  re- 
quiring consequently  31  tons  of  superphosphate. 
It  is  easy  to  bring  the  superphosphate  to  the  right 
strength  by  mixing  it  with  a  high,  grade  super- 
phosphate, or  with  gypsum  free  from  iron,  alu- 
mina, and  carbonate  of  lime.  The  low,  grade 
superphosphate  and  gypsum  act  in  the  nature  of 
a  "filler." 

In  regard  to  the  manufacture  of  superphosphate 
of  ammonia  and  potash,  this  is  prepared  in  the  same 
way.  Suppose  it  is  desired  to  prepare  a  mixture  of 
this  nature  with  5  per  cent  of  nitrogen,  7.5  per  cent 
of  potash,  and  9  per  cent  of  phosphoric  acid,  and 
that  there  was  to  be  used  for  the  purpose  sulphate 
of  ammonia  with  20.5  per  cent  N,  and  potash 
salts  with  37  per  cent  K.  To  get  100  kg.  of  super- 
phosphate of  ammonia  and  potash  it  is  therefore 


COMPOUND   MANURES  83 

necessary  to  use  -   =24.4  kg.  sulphate  of  am- 

20.5 

100  x7  5 

monia.     =  20.3  kg.  of  potash  salt  and  con- 

o«  .0 

sequently    55.3    kg.    of    superphosphate    testing 

100  X9 

=  16.27  per  cent  of  phosphoric  aicd.     Ten 
oo.o 

tons  of  the  sulphate  of  ammonia  used  would  there- 
fore give  41  tons  of  the  compound  manure.  It 
would  thus  be  necessary  to  use  31  tons  of  potash 
salts  plus  superphosphate,  say  8.32  tons  of  the 
first,  and  22.68  of  the  second.  These  manure 
mixtures  find  an  outlet  chiefly  in  regions  where  the 
vine,  tobacco,  the  hop,  and  vegetables  for  preserves 
are  cultivated.  They  are  likewise  esteemed  for 
the  culture  of  the  sugar  beet,  barley,  and  potatoes. 
Mixtures  of  superphosphate  and  potash  salts 
become  readily  moist  in  the  store,  so  that  they 
cannot  be  prepared  a  long  time  in  advance. 
The  use  of  calcined  salts  prepared  from  the 
waste  of  potash  factories,  have  the  drawback  that 
they  generally  contain  magnesium  chloride.  When 
they  are  dried  with  precaution  at  100°  C.  they 
are  free  from  basic  magnesium  compounds.  The 
retrogradation  of  the  soluble  phosphoric  acid 
in  mixed  manures  under  the  action  of  the  basic 
salts  of  potash  have  been  studied.  By  treating 
salts  of  potash  in  the  reverberatory  furnace 
to  partial  fusion,  at  about  800°  C.,  the  magnesium 
chloride  which  they  contain  is  decomposed  by  its 
water  of  crystallization.  A  molecule  of  magnesia 


84       MANUFACTURE  OF  FERTILIZING  MATERIALS 

can  retrograde  a  molecule  of  phosphoric  acid,  from 
which  it  follows  that  one  part  of  MgO  can  render 
3.55  per  cent  of  phosphoric  acid  insoluble.  If 
one  uses,  for  example,  twenty-nine  parts  of  potash 
with  2.05  per  cent  of  free  magnesia,  percentage 

2x05  X29 
controlled   by   estimation,    the    :  -=0.59 

parts  MgO  suffices  to  combine  0.59x3.55=2 
parts  of  phosphoric  acid;  as  an  actual  fact,  only 
1.4  of  insoluble  was  obtained,  which  proves  that 
the  magnesia  did  not  exert  all  its  action.  The 
cause  lies  in  the  slight  solubility  of  magnesia, 
and  in  the  fact  that  the  salts  of  potash  combine 
partially  with  the  precipitate  formed,  so  that  a 
part  of  the  phosphoric  acid  of  this  latter  remains 
in  solution. 

The  use  of  nitrate  of  soda  in  compound  ma- 
nures is  rather  restricted;  it  is  used  in  making 
nitrophosphate,  sometimes  in  nitrophosphate  of 
ammonia.  It  is  found  that  nitrate  of  soda  and 
sulphate  of  ammonia  are  incompatible,  and  that 
in  fact  it  is  better  to  use  these  manures  sepa- 
rately. Besides,  mixtures  of  superphosphate 
and  nitrate  sometimes  enter  into  spontaneous 
combustion  in  the  bags.  This  is  caused  by  the 
superphosphate  fresh  from  the  mixing  "den" 
being  mixed  with  the  nitrate  and  bagged  up 
before  it  has  had  time  to  cool.  Cold  superphos- 
phate, however  damp,  does  not  act  on  nitrate 
of  soda,  unless  in  very  warm  weather.  They 
are  no  longer  objects  of  terror  to  the  manufao- 


COMPOUND   MANURES  85 

turer,  providing  that  the  superphosphate  used 
has  been  properly  made  and  the  dry  nitrate  of 
high  percentage  mixed  with  a  superphosphate, 
likewise  dry,  does  not  give  off  nitric  acid  and  cause 
a  loss  of  nitrogen,  as  was  often  the  case  formerly 
when  superphosphate  were  wet  and  the  nitrates 
charged  with  chloride  of  sodium.  The  sodium 
chloride  decomposed  by  the  free  phosphoric 
acid  caused  the  bags  to  burst  in  transit,  for  there 
is  no  substance  which  rots  bags  like  free  chlorine 
and  fluorine,  two  elements  given  off  when  ni- 
trate and  damp  superphosphate  are  mixed. 

Finally,  a  manure  is  made  for  meadows  by 
mixing  kainit  with  superphosphate  or  with  basic 
slag.  The  mixing  entails  no  difficulty.  The  in- 
gredients are  mixed  with  a  shovel,  then  the  heap 
is  turned  over,  the  product  perhaps  passed  im- 
mediately to  the  centrifugal  crusher,  then  to 
the  sifting  machine.  If  the  kainit  be  in  blocks  or 
lumps  it  must  be  passed  to  the  crusher  to  reduce 
it  to  the  desired  fineness. 

It  has  already  been  remarked  that  in  the 
case  of  the  superphosphates  of  ammonia  of  high 
strength,  the  phosphoric  acid  soluble  in  water 
did  not  retrograde  even  when  the  superphos- 
phate entering  into  the  mixture  was  of  such 
a  nature  as  to  readily  lend  itself  to  retrograda- 
tion.  The  cause  of  this  phenomenon  is  of  both  a 
physical  and  ohemical  nature.  The  more  the 
superphosphate  is  distended  by  ballast,  which 
is  here  sulphate  of  ammonia,  the  more  distant 


86       MANUFACTURE  OF  FERTILIZING  MATERIALS 

the  particles  are  from  one  another  which  pre 
serves  their  condition.  From  a  chemical  point 
of  view,  sulphate  of  ammonia  possesses  the  prop- 
erty of  hindering  the  basic  sesquioxides  from 
precipitating  themselves,  but  it  is  clear  that  a 
retrograded  superphosphate  cannot  be  improved 
by  mixture  with  sulphate  of  ammonia. 


CHAPTER  X 
NITROGENOUS   MANURES 

THE  most  widely  distributed  nitrogenous  ma- 
nures are  nitrate  of  soda  and  sulphate  of  ammonia. 
A  third  class  of  purely  nitrogenous  manures  is 
that  represented  by  animal  waste.  These  latter 
products  are  of  considerable  agricultural  impor- 
tance, although  the  manure  trade  does  not  seem 
to  take  them  sufficiently  into  account.  These 
three  forms  of  nitrogenized  manures  are  not 
only  differentiated  by  their  chemical  compo- 
sition, but  by  their  mode  of  action  in  the  soil. 
They  form,  therefore,  three  distinct  classes,  which 
will  be  examined. 

Nitric  acid  compounds  have  been  known 
for  a  long  period.  It  is  probable,  according  to 
Herpath,  that  the  ancient  Egyptians  used  nitrate 
of  silver  to  make  their  inscriptions  on  the  bands 
in  which  they  wrapped  their  dead;  it  is  the  same 
chemical  compound  as  that  known  as  infernal 
stone,  which  is  used  to  mark  linen  and  the  skin. 
As  far  back  as  the  eighth  century  of  the  Christian 
era,  Geber  and  Marcus  described  a  body  which 
they  called  salpetrae,  which  corresponds  with 
saltpetre,  or  nitrate  of  soda.  In  the  twelfth 

87 


88      MANUFACTURE  OF  FERTILIZING  MATERIALS  ' 

century,  Raymond  Lulle  called  this  body  sal- 
nitri.  Since  then  the  term  saltpetre  has  been  used 
to  designate  nitrate  of  potash,  while  nitrate  of 
soda  is  called  Chili  saltpetre,  cr  nitre. 

Nitric  acid  consists  of  nitrogen,  oxygen,  and 
hydrogen;  its  chemical  formula  is  HN03.  It 
thus  contains  fourteen  parts  of  nitrogen  (22.2 
per  cent),  forty-eight  parts  of  oxygen  (76.19 
per  cent),  and  one  part  of  hydrogen  (1.59  per 
cent.)  It  forms  a  very  caustic  fuming  liquid. 
In  the  concentrated  state  it  has  a  density  of  1.52, 
but  the  commercial  acid  is  generally  much  weaker 
It  decomposes  easily.  It  gives  up  a  portion  of 
its  oxygen  to  oxidizable  bodies,  such  as  carbon, 
sulphur,  sulphurous  acid,  and  then  passes  to  less 
highly  oxidized  states.  Metallic  zinc  reduces 
dilute  nitric  acid,  and  converts  it  into  nitrate 
of  ammonia.  With  bases  it  forms  salts,  which 
with  the  exception  of  some  basic  metallic  salts, 
are  soluble  in  water.  Nitric  acid  is  formed  al- 
most exclusively  by  the  oxidation  of  ammonia, 
or  of  nitrogenous  matter  of  animal  origin,  under 
the  action  of  the  air  in  presence  of  bases  such 
as  the  carbonate  of  lime.  However,  this  spon- 
taneous formation  in  the  soil  is  very  slow.  It 
is,  on  the  other  hand,  very  rapid  in  Southern 
countries,  where  the  conditions  of  temperature 
and  of  moisture  in  the  air  conduce  considerably 
to  the  oxidation  of  nitrogenous  animal  matter. 

South  American  nitrate  of  soda  is  distinguished, 
more  especially  frpn^  ^ordinary  saltpetre,  by  the 


NITROGENOUS   MANURES  89 

fact  that  its  acid  is  combined  with  another  al- 
kali. In  Indian  saltpetre  it  is  combined  with 
potash,  while  in  Chili  saltpetre  it  is  combined 
with  soda.  It  is  met  with  in  the  Pampas  of  Peru, 
of  Chili  and  Bolivia,  between  19  and  27  degrees 
of  south  latitude;  it  abounds  especially  in  the 
province  of  Tarapaca  (formerly  Peruvian,  now 
Chilian),  and  in  the  desert  of  Atacama.  The 
nitrous  mineral  caliche  or  terra  saltrosa,  occurs 
as  a  layer  1  to  6  in.  thick  under  a  bed  of  con- 
glomerate, consisting  of  sand,  feldspar  and  peb- 
bles, amalgamated  by  a  cement  consisting  of 
clay  and  different  salts  forming  a  bed  20  to  30 
in.  thick.  Its  color  varies  from  gray  to  brown. 
The  conglomerate  bed  is  sometimes  wanting, 
so  that  the  mineral  crops  out  at  the  surface. 

The  caliche  is  never  pure  nitrate  of  soda. 
It  contains  mixtures  of  nitrate  of  potash,  com- 
mon salt,  iodide  and  bromide  of  sodium,  alkaline 
sulphates  and  sulphate  of  lime  mixed  with  sand. 
It  only  contains  on  an  average  25  per  cent  of 
nitrate.  Picked  pieces  contain  more. 

Opinions  differ  as  to  the  method  of  formation 
of  this  deposit  which  occupies  a  surface  of  about 
150,000  acres  and  contains  about  170,000,000 
tons.  It  is  believed  that  the  nitrate  is  formed 
from  the  nitrogen  of  guano  deposits,  which 
covered  the  shores  of  a  great  soda  water  lake 
by  a  process  analogous  to  that  to  be  seen  in 
Hungary  in  our  own  time.  The  soda  salts  of  the 
sea  water  would  simply  convert  the  saltpetre 


90       MANUFACTURE  OF  FERTILIZING  MATERIALS 

into   nitrate   of   soda.      This   opinion  has  in   its 
favor  all  the  facts  and  circumstances  met  with 


in  the  deposit.     Moreover,  traces  of  guano  are 
still  found  in  the  crude  salts.     To  extract  the 


NITROGENOUS   MANURES  91 

crude  salt  a  hole  is  dug  in  the  ground  20  in.  in 
diameter;  when  the  saltpetre  bed  is  reached  a 
chamber  35  to  40  in.  in  diameter  by  12  in.  deep  is 
excavated  and  3  to  4  cwt.  of  powder  inserted.  By 
exploding  the  powder  by  means  of  a  fuse,  a  con- 
siderable surface  of  the  deposit  is  laid  bare  often  on 
a  radius  of  40  ft.  from  the  hole.  The  crude  salt 
is  hand  picked,  to  eliminate  stones  and  frag- 
ments of  less  value;  it  is  charged  into  baskets 
or  into  trucks,  which  camels  transport  or  draw 
to  the  melting  workshop.  TO  dissolve  the  crude 
caliche  three  kinds  of  apparatus  are  used: 

1 — Open  Cast-iron  Pans — Paradas. — These  are 
heated  by  naked  fires.  Two  pans  6  ft.  6  in. 
in  diameter  are  used  for  one  furnace.  Well 
water  or  water  from  a  previous  operation  is 
run  in,  then  it  is  charged  with  caliche  or  crude 
saltpetre  reduced  to  pieces  the  size  of  the  fist. 
When  the  solution  is  concentrated  enough,  it 
is  run  into  cases  or  boxes,  where  it  clarifies;  it 
is/  then  decanted  on  the  top  of  the  depot  and 
run  into  iron  or  wooden  crystallizers;  40  per 
cent  of  crystals  is  thus  obtained  and  60  per  cent 
of  mother  liquor. 

2 — Cylindrical  Vertical  Pans — Marquinas.— 
These  are  heated  by  direct  injection  of  steam. 
They  are  26  to  33  ft.  with  a  diameter  13  to  16 
ft.  Each  of  these  pans  yields  in  24  hours,  45  to 
148  tons  of  saltpetre.  The  clarified  solution  is 
poured  into  wrought  iron  crystallizers  13  to  16 
ft.  square  and  20  in.  deep;  crystallization  requires 


92       MANUFACTURE  OF  FERTILIZING  MATERIALS 

three  to  four  days.  The  steam  given  off  contains 
an  important  amount  of  iodine  which  can  be 
avoided  by  an  addition  of  soda. 

3 — Vessels  Heated  by  a  Closed  Tubular  Bundle 
or  Steam  Coil. — This  method  has  been  introduced 
by  British  and  German  companies.  These  vessels 
measure  36  ft.  long,  6  ft.  wide  by  6  ft.  high,  into 
which  the  mother  liquor  and  the  wash  water  are 
run  and  heated  to  boiling.  Then  six  trucks  of 
perforated  wrought  iron  containing  about  four  tons 
of  caliche  are  run  in.  The  nitrate  dissolves  in 
the  water  while  the  residue  remains  in  the  trucks. 
To  hasten  solution  the  liquid  is  agitated  by  in- 
jection of  steam  and  of  hot  air  under  the  truck 
by  means  of  a  Koerting's  injector.  This  plan 
works  more  economically  than  the  preceding 
one.  At  the  same  time  the  solutions  so  obtained 
are  purer  and  more  concentrated.  To  get  a 
ton  of  nitrate  requires  three  tons  of  caliche. 
The  crystallized  nitrate  is  left  to  drain,  then  it 
is  dried  in  the  open  air.  Nevertheless  it  always 
remains  slightly  moist  owing  to  the  presence 
of  chlorides  of  calcium,  of  magnesium,  and  pos- 
sibly also  of  nitrates  of  calcium  and  magnesium, 
It  crystallizes  in  rhombohedra,  and  has  a  dirty 
reddish  gray  appearance,  due  to  its  oxide  of  iron 
content  and  to  bituminous  substances.  The 
residue  left  by  the  solution  still  contains  from 
15  to  35  per  cent  of  NaNOs.  It  is  boiled  with 
water  and  a  weak  solution  of  43°  to  45°  B.  ob- 
tained, which  is  utilized  to  dissolve  a  fresh 


NITROGENOUS   MANURES  93 

charge  of  crude  salt.  The  muds  from  the  clari- 
fication are  treated  in  the  same  way. 

Nitrate  of  soda  is  marketed  in  the  original 
sacks  weighing  254  to  308  Ib.  It  forms  a  mix- 
ture of  crystals  of  different  sizes.  It  draws  mois- 
ture from  the  air  and  when  it  \s  preserved  in 
sacks  they  rot  after  some  time  and  tear  with 
the  slightest  pull.  When  the  sacks  are  emptied, 
one  part  of  the  material,  always  moist,  remains 
adherent  to  the  fabric,  from  which  there  results 
not  only  a  loss  of  matter,  but  also  a  less  of  sacks, 
as  these  gunny  bags  then  become  unutilizable. 

Nitrate  of  soda  is  often  colored  yellow  by  the 
presence  of  chromate  of  potash  or  violet  by  the 
presence  of  nitrate  of  manganese.  The  presence 
of  nitrate  of  potash  or  magnesium  chloride  renders 
it  deliquescent,  hence  arises  loss  by  the  drainage 
of  dissolved  nitrate;  that  is  why  the  bags  are 
lodged  on  beds  of  plaster  or  clay  which  absorb 
the  liquid.  But  it  is  best  to  spread  the  nitrate 
intended  for  mixing  in  a  not  too  warm  place. 
The  bags  are  washed  with  tepid  water,  and  the 
solution  is  added  in  the  manufacture  of  super- 
phosphate which  has  to  be  mixed  with  nitrate, 
or  it  is  concentrated  in  a  pan.  Certain  manufac- 
turers content  themselves  with  beating  the  bags 
free  from  the  adherent  salt.  If  the  nitrate  ought 
to  be  employed  alone  it  is  screened  and  the  lumps 
crushed  in  a  disintegrator,  or  in  the  toothed 
roll  crusher.  It  is  dried  in  the  old  phosphate 
drier.  However,  if  it  be  stored  for  a  certain  time 


94       MANUFACTURE  OF  FERTILIZING  MATERIALS 

in  a  place  that  is  not  heated,  it  gradually  becomes 
moist.  In  consequence  of  the  risk  of  fire,  the 
building  in  which  nitrate  is  stored  should  be 
isolated  and  built  entirely  of  iron. 


CHAPTER  XI 

THE  FIXATION  OF  ATMOSPHERIC  NITROGEN, 
MANUFACTURE  OF  CYAN  AMIDE  AND  NITRATE 
OF  LIME.  EXPERIMENTS  WITH  CYANAMIDE 

ATMOSPHERIC  air  is  an  inexhaustible  source 
of  nitrogen.  It  is  calculated  that  the  column 
of  air  which  covers  two  and  a  half  acres  of 
ground  contains  79,000  metric  tons  which  gives 
or  is  equal  to  20,000  tons  of  nitrate  of  soda  per 
acre.  But  nitrogen  exists  in  the  free  state  in  the 
air,  and  to  render  it  assimilable  by  plants,  it 
is  necessary  to  convert  it  into  appropriate  com- 
pounds. We  know  that  this  conversion  can  be 
effected  by  certain  bacteria  of  the  soil,  such 
as  leguminous  bacteria,  etc.,  likewise  by  certain 
phenomena  which  occur  in  nature,  such  as 
electrical  discharges;  especially  lightning.  But 
the  amount  of  nitrogen  brought  into  the  soil 
in  this  way  is  far  from  being  sufficient  to  cover 
the  requirements,  of  plants,  and  vigorous  efforts 
are  now  being  made  to  capture  atmospheric 
nitrogen  under  an  assimilable  form.  Experi- 
ments made  enable  us  to  affirm  that  this  is 
possible.  But  all  the  tentatives  made  in  this 
direction  show  that  the  industrial  fixing  of  atmos- 
pheric nitrogen  requires  the  use  of  great 

95 


96       MANUFACTURE  OF  FERTILIZING  MATERIALS 

quantities  of  electrical  energy.  There  are  at 
present  two  chief  methods  of  manufacture:  (1) 
the  Frank  and  Caro  process,  (2)  the  Birkeland 
and  Eyde  process.  The  first  consists  in  com- 
bining atmospheric  nitrogen  dry  and  deprived 
of  its  oxygen,  with  calcium  carbide,  obtained  by 
fusion  in  the  electrical  furnace  of  equal  amounts 
of  coal  and  lime.  The  product  so  obtained  is 
termed  nitrogen  or  cyanamide  of  calcium.  The 
second  process  consists  in  oxidizing  atmospheric 
nitrogen  by  electrical  means,  and  converting  it 
into  nitric  acid,  which  is  put  into  commerce 
as  nitrate  of  lime  with  13  per  cent  of  nitrogen, 
which  has  the  greater  analogy  with  nitrate  of 
soda  and  which,  like  the  latter,  is  assimilable 
by  plants.  The  two  products  come  on  the  market 
as  more  or  less  dark,  dirty-gray  powders. 

As  just  mentioned,  this  process  for  the  man- 
ufacture of  nitrate  of  lime  consists  in  oxidizing 
atmospheric  nitrogen  by  electrical  means.  In 
1903  Prof.  Birkeland  of  Christiania  observed 
that  the  electrical  discharges  from  the  alternate 
current,  at  an  average  tension,  dispersed  in  the 
magnetic  field,  brought  about  the  combus- 
tion of  the  nitrogen  in  the  air.  This  process 
had  the  advantage  over  similar  ones  of  requir- 
ing a  much  lower  electric  tension,  say  5,000 
volts  in  place  of  15,000,  and  to  furnish  much 
higher  yields  of  nitric  acid.  The  air  is  burnt 
in  an  electrical  oven  having  the  form  of  a  drum. 
This  furnace  was  modified  and  improved  by 


FIXATION  OF  ATMOSPHERIC   NITROGEN       97 

Samuel  Eyde.  In  this  drum  the  air  is  submitted 
to  a  temperature  of  3,000°  C.  By  rapid  cooling 
the  nitrous  oxide  (NO)  formed  in  the  electric 
flame  is  retained  almost  entirely,  while  in  former 
processes  it  was  in  great  part  lost.  The  nitrous 
oxide  issuing  from  the  furnace  at  a  tempera- 
ture of  600°  to  700°  C.  combines  with  the  oxygen 
to  form  N02,  which  is  passed  through  a  series 
of  towers.  It  finally  yields  nitric  acid  of  50  per 
cent  strength,  which  is  saturated  with  lime. 
The  mass  is  heated  to  450°  C.,  which  is  its 
melting  point,  then  poured  into  cast-iron  cylin- 
ders, where  it  solidifies  slowly.  In  the  beginning, 
crystallized  nitrate  of  lime  was  manufactured 
and  was  difficult  to  use  owing  to  its  hygroscopic 
properties.  This  product  melted  between  the 
fingers  and  thus  could  only  be  used  mixed 
with  peat  dust.  That  was  why  manufacturers 
afterwards  set  themselves  to  make  basic  nitrate 
of  lime;  but  this  product  contains  only  11.7  per 
cent  of  nitrogen,  which  rendered  its  freight 
charges  heavy,  and  formed  an  obstacle  to  its 
sale.  Lately,  the  partially  dehydraded  salt 
tested  13  per  cent  of  nitrogen.  The  first  manu- 
factory of  any  importance  of  this  product  was 
built  at  Notodden  in  Norway.  The  experience 
acquired  in  that  factory  has  induced  the  manage- 
ment of  the  company  to  increase  the  plant, 
so  as  to  make  8,000  to  10,000  tons  per  annum. 
This  factory  is  maintained  by  the  Badische 
Anilin  und  Sodafabrik.  The  unit  of  nitrogen 


98      MANUFACTURE  OF  FERTILIZING  MATERIALS 

in  nitrate  of  lime  is  sold  at  the  same  rate  as  the 
nitrogen  in  nitrate  of  soda. 

Calcium  cyanamide  has  of  late  years  been 
the  subject  of  numerous  agricultural  experi- 
ments. It  must  be  observed  in  a  general  way 
that  calcium  cyanamide  neither  suits  humic 
acid  soils,  peaty  soils,  nor  light  sandy  soils. 
On  the  other  hand,  it  may  be  used  in  all  loamy 
soils  of  average  fertility.  Owing  to  the  formation 
of  dicyanamide,  this  manure  ought  to  be  spread 
at  least  eight  days  before  sowing  and  covered 
in  afterwards  in  not  too  superficial  manner.  The 
action  of  cyanamide  is  weaker  than  nitrate  of 
soda;  it  is  also  slower  than  the  latter.  But  as 
the  unit  nitrogen  is  supplied  cheaper  by  the 
new  manure,  a  greater  amount  can  be  used  to 
restore  the  balance.  Without  doubt  cyanamide 
deserves  great  attention.  According  to  the  ex- 
periments made,  this  manure  succeeds  very  well 
on  clay  soils,  but  less  so  in  sandy  soils.  It  has 
been  observed  that  the  conversion  of  cyanamide 
into  ammonia  in  the  soil  is  effected  by  bacteria, 
for  example,  by  the  B.  Megatherium  and  My- 
coid  and  other  species  in  part  new.  Nitrate  of 
lime  acts  normally  up  to  the  second  application 
in  loamy  soil  and  up  to  the  third  in  sandy  soil; 
but  beyond  that  there  is  an  injurious  action, 
especially  in  loamy  soils.  The  high  percent- 
age of  basic  nitrate  of  lime  and  the  still  higher 
percentage  of  nitrate  of  lime  produce  injurious 
effects. 


FIXATION  OF  ATMOSPHERIC   NITROGEN       99 

Nitrate  of  soda,  Chili  saltpetre  and  sulphate 
of  ammonia  have  regularly  produced  higher 
yields  and  better  utilization  of  the  nitrogen 
than  cyanamide. 

If  the  value  cf  nitric  nitrogen  be  expressed 
by  100,  the  value  of  the  nitrogen  in  cyanamide 
is  represented  by  90.  The  lime  nitrogen  acts 
a  little  more  feebly  when  it  is  decomposed  in  the 
soil,  giving  rise  to  the  formation  of  dicyanamide 
resulting  from  the  action  of  carbonic  acid,  hu- 
mic  acid,  heat  and  the  absence  of  bacteria.  The 
factors  which  favor  the  action  of  cyanamide 
are  uniform  distribution,  perfect  mixing  of  the 
manure  with  the  soil,  sufficient  moisture  to  the 
soil,  and  a  loamy  soil  rich  in  bacteria,  spreading  at 
the  latest  on  the  15th  day  of  February  for  winter 
plants. 

Cyanamide  does  not  suit  humic  acid  soils, 
where  its  action  is  uncertain  and  where  it  may 
poison  plants.  For  the  same  reason  its  use  is 
not  recommended  in  light,  sandy,  somewhat 
torpid  soils,  especially  those  with  an  acid  reac- 
tion. All  other  soils,  especially  loose  friable  soils, 
which  contain  enough  lime  and  are  regularly 
manured  with  farmyard  dung,  may  be  manured 
with  cyanamide.  The  quantity  to  use  per  acre 
is  135  to  274  lb.,  according  to  the  fertility  of 
the  soil. 

As  cyanamide  gives  off  an  enormous  amount 
of  dust  which  is  possibly  the  most  unpleasant 
defect  of  this  manure,  the  best  thing  to  do,  if 


100    MANUFACTURE  OF  FERTILIZING  MATERIALS 

a  manure  distributer  be  not  available,  is  to  mix 
it  intimately  with  double  its  weight  of  not  too 
moist  soil  and  to  spread  it  immediately.  In  no 
case  should  cyanamide  be  used  as  a  top-dressing, 
at  least  until  after  the  crop  has  been  removed, 
for  in  that  case  it  would  be  more  injurious  than 
useful. 

Stored  for  a  long  time  in  casks,  nitrate  of  lime 
suffers  considerable  loss  in  weight.  Having  been 
left  in  casks  for  five  months  it  has  been  found 
to  lose  20  to  25  Ib.  by  volatilization. 


CHAPTER  XII 

POTASSIC  MANURES.  MANUFACTURE  FROM 
CRUDE  SALT.  MANUFACTURE  FROM  FELD- 
SPAR. MANUFACTURE  FROM  SUNFLOWER 
AND  KELP  PLANTS 

THE  ash  of  plants  consists  for  the  most  part 
of  carbonate  of  potash,  the  caustic  and  deter- 
gent properties  of  which  attracted  attention 
from  the  very  beginning  of  civilization.  And 
as  a  matter  of  fact  the  ancients  knew  this  sub- 
stance and  employed  it  in  domestic  economy 
as  well  as  in  industry.  Aristotle  described  the 
manner  of  extracting  potash  from  the  ash  of 
plants.  His  process  is  still  in  use  in  certain  coun- 
tries. It  consists  in  submitting  the  ash  to  a  series 
of  washings  with  water,  concentrating  the  lye 
by  evaporation,  and  in  calcining  the  residual 
s?lt.  As  plants  leave  only  a  small  amount  of 
ash,  and  as  this  does  not  wholly  consist  of  car- 
bonate of  potash,  it  is  clear  that  the  yield  of 
potash  cannot  be  very  great. 

Carnallite  forms  the  chief  ingredient  of  crude 
potash  salts.  There  are  five  crude  salts  known 
as  Sylvinite — kainit,  schoenite,  polyhahite,  krugite 
and  carnallite. 

In  the  manufacture  of  potassium  chloride 
101 


102    MANUFACTURE  OF  FERTILIZING -MATERIALS 

(muriate  of  potash)  the  crude  salt  treated  consists 
of  a  mixture  of  all  the  salts  as  mentioned  on  previ- 
ous page.  However,  carnallite  predominates;  it 
forms  50  to  60  per  cent  of  the  crude  salt,  equal 
to  a  potassium  chloride  content  of  13  to  17  per 
cent.  The  processes  now  used  in  the  treatment 
of  the  crude  salt  in  the  manufacture  of  more 
pure  potash  salts  (potassium  chloride)  are  based 
essentially  on  the  property  of  carnallite  to  .de- 
compose in  presence  of  water  into  potassium 
chloride  and  magnesium  chloride;  it  is  therefore 
dissolved  and  potassium  chloride  separated  from 
the  solution  by  crystallization.  The  process  is 
in  itself  very  simple;  what  complicates  it  is  the 
presence  of  quite  a  series  of  foreign  salts  accom- 
panying the  carnallite,  the  most  important  of 
which  are  rock  salt  (NaCl),  in  the  proportion 
of  20  to  25  per  cent,  and  kieserite,  which  forms 
15  to  20  per  cent  of  the  crude  salt.  Other  minerals, 
such  as  kainit,  polyhalite,  tachydrite,  are  rarely 
met  with  in  large  proportion;  but  they  then 
are  very  troublesome  in  the  process. 

As  the  mines  deliver  the  crude  salt  in  big 
lumps,  which  were  at  first  delivered  ground, 
they  must  be  crushed  before  treating.  Formerly 
they  were  satisfied  with  crushing  lumps  by  blows 
from  a  mallet  with  a  long  handle,  but  now  all 
factories  have  installed  mechanical  crushers  for 
the  purpose;  the  machine  most  used  is  the  jaw- 
breaker crusher  already  described. 

The  salt  is   then  fed   into  a  pan,  in  which  it 


POTASSIC   MANURES  103 

is  dissolved.  The  crushed  salt  falls  from  the  mill 
into  the  receiver  of  a  cup-elevator  which  deliv- 
ers it  directly  into  the  dissolving  pans  or  into 
a  wrought-iron  chute.  The  elevator  is  driven 
by  a  shaft  on  which  is  mounted  the  belt  pulley. 
The  dissolving  pan  is  of  riveted  wrought-iron  of 
a  cylindrical  form  ending  in  a  conical  bottom. 
At  the  beginning  of  the  cone  is  a  perforated  short 
bottom  intended  to  retain  the  residues  from 
the  salt.  These  residues  are  run  out  through 
a  manhole.  The  solution  is  drawn  off  by  a  tap. 
The  pan  is  steam  heated.  In  the  early  days  the 
Stassfurt  and  Leopold  factories  wrought  in  an 
appreciably  uniform  style,  but  lately  they  have 
adopted  different  methods  more  conformable 
to  the  interests  of  each  factory.  The  oldest 
method,  still  much  employed,  is  the  following: 
The  dissolving  pan  is  first  partly  charged  with 
water,  mother  liquor,  which  is  termed  No.  2, 
with  residual  solution  No.  1  and  with  clarified 
solution  No.  3.  After  having  brought  this  mix- 
ture to  the  boiling-point,  by  direct  injection 
of  steam,  the  crude  salt  is  fed  into  the  elevator, 
while  continuing  to  boil  without  interruption. 
The  carnallite  soon  dissolves  and  therefore  the 
density  of  the  solution  increases  gradually.  The 
escaping  steam  by  a  suitable  arrangement  sets 
the  liquid  in  motion  and  mixes  its  different 
components.  When  the  density  of  the  liquid 
reaches  32°  to  33°  Be.,  the  elevator  is  stopped, 
the  steam  turned  off  and  the  solution  run 


104     MANUFACTURE  OF  FERTILIZING  MATERIALS 

out.  The  residue  remaining  in  the  pan  con- 
tains a  large  proportion  of  kieserite,  common 
salt,  and  about  2  to  4  per  cent  of  potash 
salts.  In  a  great  number  of  factories  this  res- 
idue is  again  taken  up  and  boiled  with  a  little 
water;  the  solution  thus  obtained  consists  there- 
fore chiefly  of  common  salt,  a  little  magnesium 
chloride  and  magnesium  .sulphate.  Its  potas- 
sium content  varies  from  3  to  7  calculated 
as  potash  chloride;  it  is  used  solely  to  dis- 
solve fresh  quantities  of  crude  salt.  The  pro- 
portions of  the  different  solutions  as  well  r.s 
the  densities  vary  with  the  factory.  The  residues 
are  thus  more  or  less  abundant  and  retain  mere 
or  less  salts.  The  best  results  are  obtained  by 
preparing  solutions  of  32°  Be.  with  lower  den- 
sities; they  retain  a  large  amount  of  common 
salt;  when  on  the  contrary  their  density  is  higher 
they  retain  less  common  salt  and  more  potas- 
sium chloride. 

The  crude  solution  as  it  comes  from  the  pan 
is  soiled  with  impurities;  it  is  therefore  run  into 
clarification  basins,  where  it  remains  for  about 
forty-five  minutes.  These  basins  are  rectangular, 
of  riveted  wrought  iron,  fitted  with  two  aper- 
tures from  one  of  which  the  clarified  solution 
is  run  off,  and  from  the  other,  the  sludge.  To 
prevent  the  clarified  solution  carrying  the  sludge 
with  it,  different  arrangements  have  been  made 
to  retain  it.  After  the  clarified  solution  has  been 
run  off,  it  is  led  through  a  wrought-iron  gutter 


POTASSIC  MANURES  105 

into  underground  crystallizers.  As  the  solution 
cools  in  flowing  through  the  gutters,  it  deposits 
a  certain  amount  of  salt  containing  45  to  50 
per  cent  of  potassium  chloride.  This  gutter 
salt  is  generally  used  in  manure  manufacture. 
It  is  generally  treated  with  potassium  chloride 
of  a  higher  strength. 

The  crystallizers  in  which  the  solution  cools 
and  forms  crystals  of  potassium  chloride  are 
of  riveted  wrought  iron  like  the  clarification 
basins;  they  vary  in  size  and  shape,  sometimes 
deep  because  they  occupy  less  space  and  yield 
larger  crystal.  When  the  solution  is  cold,  which 
takes  two  to  four  days,  the  mother  liquor  No. 
2  is  decanted  from  the  crystals  of  potassium 
chloride;  it  is  run  off  by  the  gutters  fixed  under 
the  crystallizers  into  wrought-iron  basins  or 
into  masonry  ones  lined  with  cement.  It  is 
used  either  to  dissolve  the  crude  salt  or  treated 
directly  as  will  be  described  further  on.  The 
potassium  salt  which  is  deposited  in  the  crys- 
tallizers consists  of  a  mixture  of  potassium 
chloride  and  common  salt;  it  is  still  soiled  by 
the  adhering  mother  liquor.  It  crystallizes  in 
the  same  form  as  sylvine,  with  this  difference, 
that  the  crystals  are  not  always  perfectly  formed; 
their  size  depends  chiefly  on  the  density  of  the 
solution  of  crude  salt.  When  that  has  a  density 
of  32°  to  33°  Be.  or  still  weaker  density,  crystals 
often  1  in.  wide,  of  a  pearly  lustre,  are  obtained. 
When  the  solution  is  more  dense,  say  about 


106    MANUFACTURE  OF  FERTILIZING  MATERIALS 

339  to  35°  Be.,  it  forms  soft  crystalline  needles. 
It  is  clear  that  the  size  of  these  crystals  must 
considerably  affect  the  purity  of  the  potassium 
chloride,  as  attenuated  crystals  must  retain 
more  mother  liquor  than  large  ones,  and  that 
consequently  they  contain  more  magnesium  chlo- 
ride. It  may  be  remarked  in  passing  that  the 
salt  that  is  deposited  on  the  sides  of  the  crys- 
tallizers  is  always  more  pure  than  that  deposited 
at  the  bottom.  To  obtain  high  strength  prod- 
ucts, a  portion  of  the  two  sorts  may  be  taken, 
especially  for  continuing  the  treatment. 

As  potassium  chloride  of  60  to  70  per  cent 
strength  is  hardly  marketable,  it  is  necessary 
to  submit  it  to  new  treatment — that  is,  clarifi- 
cation. For  this  purpose  it  is  run  into  vats, 
termed  clarifying  vats,  fitted  with  a  double 
bottom  covered  by  cloth  or  with  a  network  of 
osiers.  It  is  covered  with  water,  so  that  the 
water  is  2  to  3  in.  above  the  salt,  and  left  in  con- 
tact with  it  for  five  or  six  hours;  then  the  clari- 
fied solution  No.  3  is  run  off  through  a  bung- 
hole  in  the  bottom  of  the  vat.  This  liquid  runs 
into  a  special  basin,  from  which  it  is  run  into 
the  dissolving  pans  by  a  pump. 

If  the  potassium  chloride  be  not  sufficiently 
enriched  by  a  single  clarification,  this  opera- 
tion is  repeated  once  or  twice  until  the  salt  con- 
tains at  least  80  per  cent  of  dry  potassium  chlo- 
ride. The  above  clarifying  liquor  constitutes 
a  saturated  solution.  Now  a  solution  of  this 


POTASSIC   MANURES 


107 


FIG.  8.— Shark's  Teeth  taken  from  the  Hard-rock  Phosphate- 
ore  Deposits 


108     MANUFACTURE  OF  FERTILIZING  MATERIALS 

nature  contains  at  15°  C.  25  per  cent  KC1  when 
it  is  prepared  from  pure  potassium  chloride, 
27  per  cent  NaCl  when  it  is  made  from  common 
salt.  If  these  figures  be  compared  with  those 
above,  it  will  be  seen  that  the  magnesium  chlo- 
ride interferes  with  the  solution  of  both  the 
potassium  chloride  and  the  common  salt.  Now 
as  the  object  of  clarification  is  precisely  to  elim- 
inate this  latter,  it  follows  that  a  potassium  salt 
with  low  magnesium  chloride  content,  conse- 
quently large-grained,  will  be  more  easy  to 
purify  in  this  way  than  a  salt  with  high  mag- 
nesium chloride  content,  fine-grained  crystals. 
But  clarification  is  a  costly  operation  because 
its  object  is  to  redissolve  a  portion  of  the  fin- 
ished salt,  therefore  to  work  economically  it 
must  be  done  in  such  a  way  as  to  clarify  as 
little  as  possible,  that  is  to  say,  to  produce  large- 
grained  crystals  as  far  as  possible.  Starting 
from  the  salt  an  80  per  cent  product  would  be 
obtained  by  a  single  clarification,  while  a  fine- 
grain  salt  often  requires  two,  sometimes  three, 
clarifications  to  get  a  product  of  the  same  strength. 
It  is  clear  that  by  this  operation  95  per  cent 
products  and  higher  may  be  obtained. 

The  mother  liquor  not  used  for  dissolving 
is  concentrated  by  evaporation,  for  it  still  contains 
an  important  amount  of  potassium  chloride. 
In  the  evaporation  the  greater  part  of  the  com- 
mon salt  separates  out,  because  it  is  less  sol- 
uble when  hot  than  when  cold,  at  the  same 


POTASSIC   MANURES  109 

time  as  the  double  salt  of  potassium  and  mag- 
nesium, which  is  hardly  soluble.  This  mixture 
of  residual  salts  often  contains  7.5  per  cent  of 
potassium,  which  corresponds  to  12  per  cent 
of  potassium  chloride,  or  14  per  cent  of  potas- 
sium sulphate.  It  is  utilized  by  either  extracting 
the  common  salt  from  it  or  by  converting  it  into 
manure  of  low  strength.  In  rational  manufac- 
ture the  residual  salt  should  be  washed  in  the 
pan  itself;  for  this  purpose  the  mother  liquor 
No.  2  is  used,  as  the  salt  as  well  as  the  pan  itself 
is  still  very  hot.  When  the  evaporated  solution 
is  run  off,  the  mother  liquor  with  which  the 
pan  is  drenched  heats  rapidly  and  dissolves  the 
greater  part  of  the  potassium  salt  which  is  still 
contained  therein.  This  solution  is  facilitated 
by  stirring.  When  the  density  of  the  solution 
determined  while  boiling  reaches  34°  to  35°  Be., 
it  is  run  through  wrought-iron  gutters  into 
special  crystallizers,  where  it  deposits  not  po- 
tassium chloride,  but  a  salt  with  tetrahedral 
crystals,  the  composition  of  which  is  analogous 
to  carnallite.  If  the  solution  was  sufficiently 
concentrated,  the  liquid  which  flows  from  the 
carnallite  crystals  (the  final  liquid)  only  contains 
1  to  2  per  cent  of  potassium  chloride.  In  certain 
factories  the  bromine  is  extracted,  in  others 
the  magnesia.  The  artificial  carnallite  thus 
obtained  is  dissolved  in  water  in  smaller  pans 
than  those  used  to  dissolve  the  crude  salt.  The 
solution  tested  to  32°  to  33°  Be.  is  run  into  vats, 


110     MANUFACTURE  OF  FERTILIZING  MATERIALS 

where  it  deposits  potassium  chloride  more  pure 
than  that  got  from  the  crude  salt.  The  mother 
liquor  of  this  salt  is  added  to  the  first.  As  the 
carnallite  from  whence  it  comes  contains  less 
common  salt  than  the  crude  salt,  this  mother 
liquor  yields  little  residual  salt.  The  salt  yielded 
by  artificial  carnallite  is  clarified  with  very 
little  water,  and  yields  very  high  strength  potas- 
sium chloride  of  about  95  to  98  per  cent. 

In  most  factories  potassium  chloride  is  dried 
in  reverberatory  furnaces.  In  recently  erected 
factories  the  drying  is  conducted  in  cylindrical 
coil-heated  tanks,  in  which  an  agitator  with  blades 
revolves,  followed  by  a  roller  compressor.  When 
the  shaft  revolves  the  blades  turn  up  the  salt, 
and  the  roller  which  follows  makes  them  into 
a  cake  again,  so  that  the  surfaces  are  continually 
renewed.  When  the  drying  is  finished  the  salt 
is  run  out  through  a  chute  and  bagged  up.  In 
a  general  way  factories  which  work  according 
to  the  processes  described  above  are  content 
with  producing  80  per  cent  potassium  chloride; 
they  rarely  push  the  clarification  so  far  as  to 
make  97  to  98  per  cent  product,  although  the 
potassium  chloride  dissolved  by  the  clarification 
can  be  recovered  immediately  in  the  crystal- 
lizers,  while  the  mother  liquor  is  used  to  dissolve 
the  crude  salt.  To  obtain  98  per  cent  salt  with- 
out effort,  the  method  of  dissolving  the  raw 
salts  is  altered.  The  mother  liquor,  the  small 
amount  of  clarifying  liquor,  and  finally  the 


POTASSIC  MANURES  111 

liquor  used  to  boil  the  residual  salt,  are  alone 
used  as  solvent;  all  addition  of  water  is  avoided. 
After  having  brought  the  solvent  solution  in  the 
pan  to  the  boil,  the  raw  salt  is  run  in  as  before 
and  the  whole  boiled  without  interruption  until 
the  solution  tests  35°  to  36°  Be.  At  that  density 
the  carnallite  in  the  crude  salt  easily  dissolves 
if  the  liquid  be  hot  enough,  i.e.,  if  the  steam  be 
of  sufficient  tension.  Certain  factories  insert 
an  agitator  whose  action  contributes  to  mix 
the  solution,  consequently  to  obtain  a  better 
result  from  the  crude  salt.  Nevertheless,  the  res- 
idue is  sometimes  rich  in  potassium  chloride; 
and  is  boiled  a  second  time  with  pure  mother 
liquor.  The  solution  so  obtained  is  clarified  in 
the  same  way  as  in  the  first  method;  on  cooling, 
it  deposits  not  potassium  chloride  but  carnal- 
lite,  which  is  allowed  to  drain  and  then  dissolve 
in  boiling  water  to  extract  the  potassium  chloride. 
As  common  salt,  as  well  as  kieserite,  dissolves  only 
slightly  when  hot  in  a  concentrated  solution 
of  magnesium  chloride,  while  potassium  chloride  is 
very  soluble  therein,  it  is  clear  that  the  solu- 
tion prepared  by  this  process  should  contain 
very  little  common  salt,  and  also  that  the  car- 
nallite which  crystallizes  therefrcm  should  contain 
very  little,  and  the  chloride  of  potassium  fur- 
nished by  the  latter  should  be  of  high  strength. 
This  method,  however,  has  the  drawback  of 
yielding  a  large  amount  of  carnallite,  the  re- 
moval and  solution  of  which  require  much  labor 


112    MANUFACTURE  OF  FERTILIZING  MATERIALS 

and  steam  and  consequently .  fuel.  This  draw- 
back is  obviated  by  diluting  the  solution  which 
flows  from  the  clarification  vats,  with  water, 
so  that  after  complete  cooling  it  yields  chloride 
of  potassium  of  high  strength  directly,  and 
no  longer  carnallite.  In  this  way  the  crystalli- 
zation and  solution  of  carnallite  is  conducted 
in  a  single  operation.  The  advantages  of  this 
method  of  working  are  evident:  Instead  of  treat- 
ing as  before,  two  different  solutions  and  two 
different  salts,  only  a  single  solution  and  a  single 
salt  have  now  to  be  treated.  /The  potassium 
chloride  so  produced  is  so  pure  that  when  it 
is  freed  from  magnesium  chloride  by  a  little 
water,  it  contains  only  0.5  per  cent  of  common 
salt,  all  the  rest  being  potassium  chloride  with  a 
little  moisture  and  some  slight  impurities. 

In  the  manufacture  of  potassium  sulphate, 
the  process  is  by  drenching  potassium  chloride 
with  sulphuric  acid  and  calcining  in  a  rever- 
beratory  furnace.  The  reaction  which  takes 
place  is  the  same  as  that  used  to  manufacture 
sodium  sulphate  from  common  salt  and  sul- 
phuric acid.  First  of  all  the  material  heats, 
gaseous  hydrochloric  acid  is  given  off,  and  acid 
potassium  sulphate  formed.  Afterwards  the 
temperature  continuing  to  rise,  the  acid  sulphate 
of  potassium  being  weak  acts  on  the  remainder  of 
the  potassium  chloride.  A  new  disengagement 
of  hydrochloric  acid  gas  is  produced,  and  finally 
potassium  sulphate  remains  as  a  solid  mass.  As 


POTASSIC   MANURES  113 

the  potassium  sulphate  as  it  comes  from  the 
furnace  is  in  big  lumps,  it  must  be  crushed  before 
delivery  to  the  farmer.  In  the  same  way  as  the 
price  of  potassium  chloride  is  calculated  on 
the  basis  of  an  80  per  cent  salt,  that  of  potassium 
sulphate  is  based  on  a  90  per  cent  salt,  conse- 
quently 100  Ib.  of  this  product  at  95  per  cent 
equals  110  Ib.  at  90  per  cent. 

About  90  patents  have  been  issued  by  the 
United  States  Government  for  extracting  potash 
from  silicate  rocks.  At  least  four  may  be  con- 
sidered modifications  of  the  J.  Lawrence  Smith 
method,  since  the  essential  feature  of  each  con- 
sists in  heating  the  potash — bearing  material 
with  calcium  carbonate  and  some  metallic  chlo- 
ride. 

The  first  of  these,  United  States  Patent  No. 
513,001,  was  issued  to  H.  S.  Blackmore  in  1894. 
To  produce  a  soluble  potassium  salt  according 
to  this  patent,  orthoclase,  reduced  to  a  fine 
powder,  is  mixed  with  finely  powdered  calcium 
chloride  in  about  equal  proportions  to  the  po- 
tassium silicate  present.  To  the  mixture  is  then 
added  an  excess  of  calcium  oxide  and  a  sufficient 
quantity  of  water  to  render  the  entire  mass 
moist.  This  is  introduced  into  a  sealed  furnace, 
or  retort  and  heated  to  a  temperature  of  about 
1100°  C.,  whereby  the  water  mixed  with  the 
mass  is  converted  into  superheated  steam  at 
high  pressure,  which  is  supposed  to  assist  ma- 
terially in  the  transformation  of  the  orthoclase  into 


114     MANUFACTURE  OF  FERTILIZING  MATERIALS 

soluble  potassium  chloride  and  insoluble  sili- 
cates of  calcium  and  aluminium.  The  heating 
is  continued  for  about  two  hours,  and  after 
cooling  the  mass  is  placed  in  vats  and  lixiviated. 

The  part  of  the  process  as  patented  which 
requires  the  moist  mass  to  be  heated  in  a  sealed 
furnace  to  a  temperature  of  1100°  C.,  could 
obviously  not  be  carried  out  on  a  large  scale, 
for  it  would  not  be  feasible  to  make  a  furnace 
which  would  stand  the  pressure  produced  at 
this  temperature. 

In  1900  United  States  Patent  No.  641,406 
was  granted  to  G.  J.  Rhodin  for  obtaining  sol- 
uble potassium  from  feldspar.  In  carrying  out 
the  process  according  to  this  invention,  1  part 
of  feldspar  is  mixed  with  1  part  of  lime  and  0.2 
part  of  sodium  chloride,  all  in  a  finely  powdered 
condition.  The  mixture  is  then  heated  in  a 
closed  vessel  of  iron  or  other  material,  or  else 
in  an  open-hearth  or  blast  furnace,  to  a  bright 
yellow  heat  and  maintained  at  that  temperature 
for  a  considerable  time,  care  being  taken  not  to 
melt  or  fuse  the  mixture.  The  cooled  mass 
which  still  remains  in  a  powder  may  be  applied 
directly  as  a  manure,  since  the  potash  is  claimed 
to  be  rendered  available  by  the  treatment,  or 
it  may  be  separated  from  the  mass  by  treatment 
with  acids. 

In  1907  United  States  Patent  No.  869,011 
was  issued  to  Ralph  H.  McKee  for  a  process 
for  obtaining  potassium  compounds  from  potash- 


POTASSIC  MANURES  115 

bearing  material  containing  mica  by  essentially 
the  same  treatment  as  that  covered  by  Rhodin's 
patent  for  the  extraction  of  potash  from  feldspar. 
United  States  Patent  No.  987,436  was  granted 
to  A.  S.  Cushman  in  1911  for  a  method  for  ob- 
taining potash  from  silicate  rocks.  According 
to  this  method  the  feldspathic  rock  is  reduced 
to  as  fine  a  subdivision  as  possible  and  mixed 
with  finely  powdered  quicklime  in  the  proportion 
of  100  parts  of  the  rocks  to  20  parts  of  lime. 
The  mixture  is  then  spread  on  a  suitable  con- 
veyor, as  belt  or  drum,  in  the  form  of  a  bed 
having  a  thickness  from  three-eighths  to  one- 
half  inch.  To  the  surface  of  this  bed  is  applied 
a  solution  of  calcium  chloride  in  separate  drops 
and  of  such  a  concentration  that  the  amount  of 
calcium  chloride  added  should  be  sufficient  to 
supply  chlorine  in  quantities  at  least  molecularly 
equivalent  to  the  total  alkali  contained  in  that 
portion  of  the  feldspar  which  becomes  aggre- 
gated into  lumps  on  the  addition  of  solution. 
The  aggregates  which  harden  quickly  at  or- 
dinary temperatures,  are  separated  from  the  un- 
converted powder  by  screening,  and  then  heated 
in  a  rotary  kiln  at  a  temperature  preferable, 
but  not  necessarily,  below  the  point  at  which 
a  substantial  part  of  the  potassium  chloride  is 
sublimed.  The  product  is  discharged  contin- 
uously from  the  furnace  in  lumps  and  may  be 
crushed  for  use  directly  as  a  fertilizer;  or  the 
potassium  chloride  may  be  extracted  by  means 


116     MANUFACTURE  OF  FERTILIZING  MATERIALS 

of   water   and   recovered   from   the   solution,    or 
utilized  there  in  any  preferred  way. 

From  a  comparative  study  which  was  made  of 
these  patents  it  does  not  appear  that  the  use 
of  sodium  chloride  has  any  advantage  over 
calcium  chloride.  The  latter  is  a  by-product 
obtained  in  large  quantities  in  the  manufacture 
of  sodium  carbonate,  and  is  somewhat  more  ef- 
fective than  the  former  in  bringing  about  com- 
plete decomposition  of  the  feldspar,  but  when 
limited  amounts  of  'the  reagents  are  used  more 
potash  is  rendered  soluble  with  the  use  of  sodium 
chloride  than  with  calcium  chloride. 

In  these  experiments  the  results  show  that 
while  a  considerable  portion  of  the  potash  was 
rendered  available  when  using  approximately 
the  proportions  of  the  reagents  stated  in  the  pat- 
ents the  total  potash  in  the  feldspar  was  not 
rendered  soluble  in  this  way  at  the  temperature 
specified.  Thus,  when  1  part  of  the  feldspar 
is  ignited  with  1  part  of  calcium  carbonate  and 
0.25  part  of  calcium  chloride,  which  is  0.05 
part  in  excess  of  that  equivalent  to  the  alkalis 
in  the  feldspar,  only  about  60  per  cent  of  the 
potash  in  the  feldspar  is  rendered  soluble.  In- 
creasing the  proportions  of  calcium  carbonate 
and  calcium  chloride  used  produces  a  compara- 
tively small  increase  in  the  amount  of  soluble 
potash  obtained,  and  complete  decomposition 
of  the  feldspar  only  takes  place  when  one  part 
is  ignited,  under  the  conditions  of  the  experi- 


POTASSIC   MANURES  117 

merit,  with  about  1  part  of  calcium  chloride 
and  about  2  to  3  parts  of  lime.  When  this  pro- 
portion of  the  reagents  is  used,  considerable 
variation  in  the  temperature  of  ignition  will 
give  the  same  results,  and  almost  the  entire 
amount  of  the  potash  is  rendered  soluble  at 
a  temperature  below  the  melting-point  of  po- 
tassium chloride. 

The  results  obtained  on  igniting  feldspar 
with  lime  and  sodium  chloride  are  in  agreement 
with  those  published  by  Rhodin,  the  author 
of  the  patent  covering  this  process,  who  only 
claimed  an  extraction  of  about  14  per  cent  of 
the  potash  in  the  feldspar  when  using  the  pro- 
portion of  the  reagents  stated  in  the  patent.  It 
was  pointed  out,  however,  that  a  more  favorable 
result  was  obtained  by  using  a  larger  amount 
of  salt  with  a  smaller  amount  of  lime.  Thus, 
when  100  parts  of  feldspar  were  ignited  to  900° 
C.  with  40  parts  of  salt,  about  70  per  cent  of  the 
potash  in  the  feldspar  became  soluble,  which 
agrees  with  the  values  given  for  approximately 
this  proportion  of  the  reagents. 

Unless  a  large  excess  of  calcium  chloride 
is  used,  when  ignited  with  feldspar  and  lime, 
no  vitrification  takes  place  on  heating  to  a  tem- 
perature up  to  1050°  C.  The  ignited  mass  re- 
mains in  the  form  of  a  powder,  and  consequently 
the  soluble  material  present  can  be  readily 
leached  out  without  the  necessity  of  any  previ- 
ous grinding  of  the  mass.  The  same  statements 


118    MANUFACTURE  OF  FERTILIZING  MATERIALS 

hold  true  when  sodium  chloride  is  used,  bub 
with  a  more  limited  variation  in  the  proportion 
of  the  reagents  which  may  be  taken.  Thus, 
a  hardened  mass  is  obtained  when  1  part  of 
feldspar  is  ignited  to  1050°  C.,  with  1  part  of 
calcium  carbonate  and  0.25  part  of  sodium  chlo- 
ride, but  if  the  proportion  of  calcium  carbonate 
is  doubled  the  mass  remains  in  a  powdered  form. 
When  calcium  chloride  is  used,  the  mass  does 
not  harden  on  ignition,  even  with  1  part  of  cal- 
cium carbonate. 

On  account  of  its  simplicity,  the  method  of 
decomposing  feldspar  by  heating  with  calcium 
carbonate  and  with  calcium  chloride  (or  sodium 
chloride)  could  undoubtedly  be  carried  out  on 
a  large  scale  without  involving  any  serious  me- 
chanical difficulty,  and  the  method  would  thus 
be  a  practical  one  providing  the  value  of  the 
products  obtained  would  compensate  for  the 
expense  involved.  Although  pure  feldspar  may 
be  obtained  which  contains  upward  of  15  per 
cent  potash,  the  average  grade  of  feldspar  which 
could  be  mined  on  a  large  scale  would  undoubtedly 
contain  less  than  10  per  cent.  If  potash  be  quoted 
at  sixty-six  cents  a  unit,  then  potash  in  a  ton  of 
feldspar  containing  even  10  per  cent  of  this 
constituent  would  be  worth  only  $6.60  when 
converted  into  the  soluble  form.  It  is  then  evi- 
dent that  the  value  of  the  potash  alone  will 
not  compensate  for  its  extraction,  or  by  any 
modification  of  it  for  which  patents  have  been 


POTASSIC  MANURES  119 

granted;  nor  is  it  at  all  likely  in  view  of  the 
comparatively  low  percentage  of  potash  in  all 
silicate  rocks  that  any  process  can  be  devised 
which  will  prove  so  simple  that  the  value  of  the 
potash  alone  will  pay  for  its  extraction.  So  far 
as  I  ani  informed  these  processes  have  never  been 
practical  on  account  of  the  fact  that  in  all  of 
them  the  cost  of  producing  the  potash  is  greater 
than  its  market  value.  It  may  be  that  on  account 
of  the  European  War  some  of  these  processes  will 
become  commercially  feasible.  It  seems  safe  to 
say,  therefore,  that  any  method  to  be  economical 
must  produce  at  the  same  time  other  products 
of  value  in  addition  to  the  potassium. 

In  a  modification  of  the  old  Charles  Bickell 
process,  it  has  been  shown  that  all  the  corstitu- 
ents  of  pure  feldspar-lime  clinker  lie  between  the 
limits  allowable  in  a  good  Portland  cement,  and 
that  ferric  oxide  is  the  only  necessary  constituent 
absent.  If  commercial  feldspar  and  lime  were 
used,  however,  this  would  no  doubt  also  be  sup- 
plied in  sufficient  quantity,  and  at  the  same  time 
the  silica  and  lime  would  be  reduced  more  closely 
to  the  mean  of  that  found  in  good  Portland  cement, 
providing  the  feldspar  does  not  contain  an  exces- 
sive amount  of  free  silica. 

In  order  that  a  clay  may  be  suited  for  the  manu- 
facture  of  cement  it  should  have  a  percentage  ratio 
of  silica  to  alumina  of  from  3  to  1  or  4  to  1.  The 
ratio  of  these  two  constituents  in  feldspar  is 
3,5  to  1.  In  muscovitc  and  leucite  of  theoretical 


120    MANUFACTURE  OF  FERTILIZING  MATERIALS 

composition,  the  proportion  of  silica  to  alumina 
is  less  than  3  to  1,  but  in  commercial  samples  of 
leucite-bearing  rocks,  the  ratio  is  usually  greater 
than  4  to  1. 

A  clinker  of  the  same  ultimate  composition  as 
that  which  results  when  feldspar  and  lime  are 
heated  together  may  also  be  obtained  when  part 
of  the  lime  is  replaced  by  sufficient  calcium  chloride 
to  be  equivalent  to  the  potash  and  soda  in  the 
feldspar,  the  total  calcium  used  remaining  the 
same  as  before;  in  carrying  out  this  experiment, 
the  feldspar  and  lime  were  ignited  to  constant 
weight,  and  the  calcium  chloride  thoroughly  dried 
by  heating  in  an  air  bath  below  its  melting-point. 
Ten  grams  of  the  feldspar  were  well  mixed  with 
2.0050  grams  of  calcium  chloride  and  15.7895 
grams  of  calcium  oxide,  and  the  mixture  then 
ignited  in  an  open  dish  in  the  furnace  at  1400°  C. 
By  this  treatment  the  alkalies  are  volatilized  as 
the  chlorides.  On  igniting  for  one-half  hour,  the 
weight  lost  by  the  ignited  mass  amounted  to 
2.5632  grams,  equal  to  25.63  per  cent  of  the 
feldspar.  When  expressed  as  the  chlorides,  the 
percentage  of  alkalies  in  the  feldspar  used, 
amounted  to  25.82  per  cent.  It  would  appear, 
therefore,  that  practically  the  whole  of  the  al- 
kalies in  the  feldspar  were  volatilized  during  the 
first  half  hour  of  ignition.  On  continuing  the-, 
ignition  for  one  hour  longer,  the  additional  decrease 
in  weight  which  took  place,  amounted  to  only 
0.0090  gram,  The  residue  was  then  analyzed  for 


POTASSIC  MANURES  121 

potassium  and  chlorine,  but  only  a  small  trace  of 
each  was  found. 

That  shows  that  the  volatilization  of  the  potash 
in  feldspar  takes  place  more  rapidly  when  part 
of  the  lime  is  replaced  by  calcium  chloride  than 
when  feldspar  is  ignited  with  it  alone,  but  in 
each  case  the  ultimate  composition  of  the  residue 
obtained  is  the  same.  Any  excess  of  calcium 
chloride  used  above  that  equivalent  to  the  potas- 
sium in  the  feldspar  is  slowly  decomposed  at  the 
temperature  at  which  the  ignitions  were  made, 
leaving  behind  the  oxide  of  calcium. 

Since  the  clay  used  in  making  cement  contains 
in  some  cases  as  high  as  3  or  4  per  cent  of  potash, 
it  might  be  expected  that  part  would  escape  from 
the  kiln  and  be  collected  with  the  flue  dust 
(particularly  in  those  plants  where  a  process  for 
collecting  dust  has  been  installed:  This  has  been 
observed  by  several  investigators  to  really  take 
place),  and  the  potash  then  collected  is  found  to 
be  in  a  soluble  form.  By  the  substitution  of 
feldspar  for  clay  in  the  manufacture  of  cement, 
the  potash  then  collected  would,  no  doubt,  be 
greatly  increased,  but  since  the  analyses  of  cement 
show  the  presence  of  alkalies,  it  follows  that  with 
the  style  of  kilns  now  in  use  all  the  potash  in 
feldspar  could  not  be  made  available  in  this  way, 
and  that  a  larger  proportion  of  the  potassium 
would  be  volatilized  by  substituting  for  a  part 
of  the  lime,  sufficient  calcium  chloride  to  be 
equivalent  to  the  potassium,  is  evident  from  the 


122    MANUFACTURE  OF  FERTILIZING  MATERIALS 

experiments    already    referred    to,    and    experi- 
ments are  now  being  taken  on  a  large  scale  to 
•compare  the  practicability  of  this  procedure  with 
the  simple  ignition  of  feldspar  and  lime  alone. 

According  to  census  reports  of  1910,  the  Port- 
land cement  manufacture  in  the  United  States 
during  the  year  1909,  amounted  to  65,000,000 
barrels,  or  13,000,030  tons,  valued  at  approxi- 
mately $53,000,000.  The  maximum  quantity  of 
potash  which  it  would  be  possible  to  obtain  by 
the  use  of  feldspar  in  the  manufacture  of  this 
quantity  of  cement  can  be  calculated  if  the  potash 
content  of  the  feldspar  is  known.  This  varies 
from  about  16  per  cent  down  to  less  than  8  per 
cent,  but  if  8  per  cent  be  taken  as  the  average 
percentage  of  potash  in  commercial  feldspar,  then 
1  part  of  feldspar  combined  with  3  parts  of  cal- 
cium carbonate,  equal  to  1.68  parts  of  calcium 
oxide,  would  yield  0.08  part  of  potash  and  2.6 
parts  of  cement.  Therefore,  13,000,000  tons  of 
cement  would  produce  400,000  tons  of  potash. 
Again,  quoting  potash  at  66  cents  per  unit,  this 
would  have  a  value  of  $26,400,000,  which  is 
three  times  the  value  of  the  potash  salts  used  in 
this  country  during  the  year  referred  to,  and 
about  twice  the  value  of  the  imports  for  1911. 
Whether  or  not  this  would  cover  the  cost  of  the 
feldspar,  its  transportation,  and  the  expense  inci- 
dent to  the  recovery  of  the  potash,  can  only  be 
determined  by  experimentation  on  a  large  scale; 
but  the  probability  that  potash  salts  can  thus  be 


POTASSIC  MANURES  123 

obtained  in  large  quantities  as  a  by-product  maker 
this  method  of  getting  at  the  potash  in  feldspas 
quite  promising. 

In  the  manufacture  of  potash  in  the  Cau- 
casus from  the  sunflower  plant,  the  ashes  of 
the  stem  and  the  branches  of  the  sunflower 
yield  the  raw  material.  The  first  potash  factory 
was  established  in  1899  at  Maikopp,  by  Schapo- 
nalow.  Difficulties  occurred  at  first  because 
experience  was  wanting.  But  gradually  the 
conditions  of  production  improved,  and  new 
factories  were  started.  According  to  the  official 
statistics  in  1907,  11  of  these  factories  produced 
475,563  poods  of  potash.  According  to  informa- 
tion supplied  by  the  manufacturers  twenty-four 
factories  were  in  operation  in  1908,  and  some 
of  them  produced  from  several  thousands  up  to 
200,000  poods  of  potash.  The  total  production 
of  these  factories  was  from  700,000  to  900,000 
poods,  representing  a  value  of  22,000,000  rubles. 
The  stems  of  the  sunflower  are  generally  burnt 
by  the  farmers  themselves.  But  certain  manu- 
facturers also  burn  the  plant  buying  the  stems 
of  10,000  to  15,000  deciatines,  for  which  they 
pay  3  to  4  rubles  per  deciatine.  A  deciatine  of 
sunflower  yields  in  good  ground  200  to  300  poods 
of  stems  and  in  bad  ground  100  poods  only, 
from  which  3  to  5  per  cent  of  ashes  may  be  ex- 
tracted, and  3  to  4  poods  of  ashes  give  one  pound 
of  potash.  The  percentage  of  carbonate  of  potash 
is  20  to  35  per  cent.  The  appearance  of  the  ash 


124    MANUFACTURE  OF  FERTILIZING  MATERIALS 

is  improved  by  a  few  turns  of  the  wrist,  by 
throwing  the  salt  in  the  fire  for  instance,  which 
causes  the  ash  to  fuse  and  gives  it  a  vitreous 
appearance. 

When  the  sunflower  harvest  is  finished  the 
stems  are  burnt.  The  purchase  of  ashes  is  fin- 
ished in  September,  while  the  manufacture  of 
potash  lasts  five  to  six  months.  The  price  of  the 
ashes  up  to  now  have  been  35  copecks,  but  owing 
to  competition  it  has  risen  to  40  and  60  copecks 
per  pood.  The  manufacture  of  potash  is  con- 
ducted in  a  very  primitive  fashion;  it  consists 
in  lixiviating  the  ashes,  methodically  concentrat- 
ing the  lye,  and  in  calcining  the  product.  The 
product  is  packed  in  casks  of  30  to  40  poods. 
The  analysis  of  potash  from  Kuban  gave,  water, 
1.74  per  cent;  carbonate  of  potash,  89  per  cent; 
carbonate  of  soda,  5.0  per  cent;  sulphate  of  pot- 
ash, 2.01;  -potassium  chloride,  6.51  per  cent; 
insoluble  by  difference,  0.74  per  cent;  the  usual 
potassium  carbonate  content  is  90  to  91.  It  is 
dealt  with  on  a  basis  of  90  per  cent  with  2  per 
cent  margin  at  least.  Three-fourths  of  the  pot- 
ash is  exported  to  Hamburg,  London  and  New 
York  City. 

Upon  the  same  principle  as  that  dealt  with 
and  described  in  the  manufacture  of  potash 
from  the  sunflower,  potash  could  be  manufactured 
from  the  seaweed  known  as  kelp.  For  a  long 
time  it  has  been  used  and  known  in  the  crude 
state  as  an  excellent  dressing  for  land.  Experi- 


POTASSIC   MANURES  125 

ments  that  have  been  made  along  the  line  as 
described  for  the  sunflower  plant,  show  that 
from  50  tons  of  kelp  weed,  five  tons  of  20  per 
cent  potash  content  have  been  realized.  If  this 
process  was  practiced  in  the  United  States 
under  the  present  stringency  of  potash  shipments 
from  Europe  due  to  the  embargo  laid  on  potash 
on  account  of  the  European  War,  it  might  have 
an  effect  in  relieving  the  farming  conditions  in  this 
country  as  they  exist  at  present  due  to  the  high 
price  of  fertilizers.  No  experiments  that  have 
come  under  the  observation  of  the  writer  give 
any  data  of  the  expense  of  recovering  the  kelp 
weed  from  the  sea.  It  may  be  that  future  data 
will  be  forthcoming  that  will  make  this  an 
industry  in  the  United  States  of  a  permanent 
character. 


CHAPTER  XIII 

ON  THE  EXAMINATION   OF   COMMERCIAL  FER- 
TILIZERS AND   MATERIALS 

THE  methods  here  given  necessarily  include 
the  examination  of  material  used  in  the  manu- 
facture of  fertilizers. 

Moisture. — Inasmuch  as  the  percentage  of 
moisture  in  a  fertilizer  may  vary  considerably 
under  the  conditions  to  which  it  is  exposed, 
a  determination  of  moisture  is  always  imperative, 
in  order  that  the  results  on  other  constituents 
as  determined  by  different  analysts,  say  those  of 
the  buyer  and  the  seller,  may  be  fairly  compared. 

Some  analysts  invariably  heat  to  a  certain 
temperature  (100°  to  110°  C.)  until  a  constant 
weight  is  obtained;  others  heat  for  a  certain 
time,  2,  3,  or  5  hours,  and  call  the  loss  moisture. 
The  plan  prescribed  by  the  Association  of  Official 
Agricultural  Chemists  is  probably  most  uni- 
formly followed.  That  is  as  follows: 

For  alkaline  salts,  heat  1  to  5  gms.  at  130° 
to  constant  weight. 

For  other  material,  heat  2  gms.  (or  5  gms. 
if  the  sample  be  coarse)  for  five  hours  at  100°. 
The  loss  in  either  case  is  taken  as  representing 
moisture. 

126 


EXAMINATION  OF  COMMERCIAL  FERTILIZERS     127 

Phosphoric  Acid. — The  phraseology  regarding 
the  phosphoric  acid  in  fertilizers  is  often  confus- 
ing. As  may  have  been  inferred,  three  forms 
of  phosphoric  acid  are  recognized  in  fertilizers,  viz. : 

1. — That  readily  soluble  in  water,  consist- 
ing presumably  of  calcium  "superphosphate" 
(CaH4(P04)2). 

2. — That  not  readily  soluble  in  water,  but 
soluble  in  certain  organic  solutions,  presumably 
consisting  of  CaH(PO4)  or  acid  ferric  and 
aluminic  phosphates. 

3. — That  insoluble  both  in  water  and  in  the 
solvents  for  No.  2,  remaining  presumably  in 
the  condition  in  which  it  originally  existed  in 
the  phosphate  rock. 

Notwithstanding  the  fact  of  there  being 
numerous  possible  combinations  between  phos- 
phoric acid  and  lime  in  a  fertilizer,  it  is  often 
required  that  a  report  shall  show  the  amount 
of  "bone-phosphate,"  to  which  any  given  per- 
centage of  phosphoric  acid  is  equivalent.  The 
percentage  of  phosphoric  acid  multiplied  by  the 
factor  2.1831  will  give  the  desired  figure. 

No.  1  is  called  "soluble  phosphoric  acid"  or 
"water-soluble  phosphoric  acid." 

No.  2  has  been  called  "  reverted,  inverted, 
reduced,"  etc.,  phosphoric  acid,  or,  because  it 
is  usually  determined  by  washing  it  out  with 
a  solution  of  ammonium  citrate,  it  has  been 
called  "  citrate  soluble." 

The   sum  of   Nos.   1  and  2  is  usually  meant 


128    MANUFACTURE  OF  FERTILIZING  MATERIALS 

when  the  term  "available"  phosphoric  acid  is 
employed.  English  analysts  usually  apply  the 
term  "available"  as  a  synonym  for  "water  sol- 
uble," and,  on  the  other  hand,  the  term  "sol- 
uble" is  also  sometimes  used  when  the  sum  of 
No.  1  and  No.  2  is  meant. 

No.  3  is  usually  called  "insoluble,"  but  to 
express  it  more  exactly  it  has  also  been  called 
"citrate  insoluble." 

Much  of  this  confusion  of  terms  has  arisen 
from  the  diversity  of  opinion  as  to  the  utility 
of  the  different  forms  in  which  the  phosphoric 
acid  may  be  combined. 

The  sum  of  Nos.  1,  2,  and  3  is  called  "total 
phosphoric  aciti." 

Total  Phosphoric  Acid. — The  phosphoric  acid 
is  usually  separated  as  the  molybdate  compound, 
which  is  dissolved  in  ammonia,  and  precipitated 
for  weighing  by  magnesium  mixture. 

As  the  organic  matter  of  the  fertilizer  would 
interfere  with  the  complete  separation  of  the 
phospho-molybdate,  it  must  be  destroyed  (usu- 
ally by  ignition,  with  or  without  the  addition 
of  some  nitrate).  Hydrochloric  acid  is  the  best 
solvent  for  ignited  phosphates,  but  the  molyb- 
date precipitation  is  best  made  in  a  nitric  acid 
solution,  so  that,  although  after  ignition  hydro- 
chloric acid  must  be  used  to  effect  solution, 
nitric  acid  and  nitrates  should  largely  predom- 
inate when  the  molybdate  separation  is  effected. 

Weigh  out  2  gms.  of  the  sample  in  a  platinum 


EXAMINATION  OF  COMMERCIAL  FERTILIZERS     129 

dish,  wet  down  with  5  cc.  of  magnesium  nitrate 
solution  (600  gms.  per  litre),  dry,  and  ignite. 
Ignition  without  addition  of  nitrate  seldom  in- 
duces error,  but  is  usually  slower.  After  cooling, 
treat  with  5  to  10  cc.  of  hydrochloric  acid,  heat, 
then  transfer  to  a  beaker;  add  about  30  cc.  of 
nitric  acid,  boil  and  filter.  When  the  fertilizer 
contains  much  iron  and  alumina  more  hydro- 
chloric acid  should  be  used.  If  made  up  with 
phosphoric  slags,  gelatinous  silica  will  appear, 
which  requires  evaporation  to  dry  ness,  and 
taking  up  with  hydrochloric  acid. 

A  method  recommended  for  fertilizers  con- 
taining very  large  quantities  of  organic  matter, 
consists  in  boiling  with  20  to  30  cc.  of  concen- 
trated sulphuric  acid  in  a  Kjeldahl  flask,  adding 
crystals  of  sodium  or  potassium  nitrate  from  time 
to  time  until  the  organic  matter  is  destroyed, 
diluting  and  filtering.  The  presence  of  much 
sulphuric  or  hydrochloric  acid  retards  the  sepa- 
ration of  the  molybdate  precipitate,  and  is  best 
avoided.  Hydrochloric  acid  can  be  removed  by 
evaporating  low  with  excess  of  nitric  acid;  sul- 
phuric acid,  however,  cannot. 

In  any  case,  dilute  the  clear  solution  to  200 
cc.,  mix  well,  and  take  50  cc.  for  the  analysis 
(representing  0.4  gm.)  With  phosphate  rock, 
half  this  amount  will  suffice. 

Add  ammonia  until  it  is  just  alkaline,  then 
acidify  decidedly  by  addition  of  5  cc.  of  nitric 
acid;  add  10  to  15  gms.  of  ammonium  nitrate 


130    MANUFACTURE  OF  FERTILIZING  MATERIALS 

crystals,  warm  to  80  or  90°  C.  and  add  molyb- 
date  solution  in  the  proportion  of  50  cc.  for 
every  0.1  gm.  of  phosphoric  acid  assumed  to  be 
present.  For  ordinary  fertilizers  which  contain 
less  than  20  per  cent  phosphoric  acid,  50  cc.  will 
be  ample.  Let  stand  warm,  with  frequent  stirring, 
until  the  precipitate  settles  readily  when  dis- 
turbed; wash  by  decantation  with  cold  dilute 
solution  of  ammonium  nitrate  acidified  with 
nitric  acid,  allowing  as  little  as  possible  of  the 
precipitate  to  get  on  the  filter.  Dissolve  the  pre- 
cipitate in  ammonia,  and  precipitate  by  mag- 
nesia mixture,  adding  it  slowly  to  the  clear 
solution,  which  is  vigorously  stirred.  Let  stand 
cold  for  30  minutes. 

Filter  upon  an  ashless  filter,  wash  with  water 
containing  one-eighth  its  volume  of  ammonium 
hydroxide,  dry,  ignite  at  first  with  gentle  heat, 
finally  at  red  heat,  in  a  porcelain  crucible  to 
constant  weight,  and  weigh  as  magnesium  pyro- 
phosphate. 

After  ignition  this  precipitate  should  be 
white  or  light  gray  in  color. 

Water-soluble  Phosphoric  Acid.  —  Place  2  gms. 
of  the  well-ground  and  mixed  sample  in  a 
9-cm.  filter  and  wash  with  successive  portions 
of  water,  say  15  to  20  cc.  at  a  time,  allowing 
each  lot  to  run  off  before  the  next  is  added,  until 
the  washings  measure  250  cc.  If  the  washings 
contain  but  little  organic  matter,  one-fifth  of 
the  filtrate  may  be  used  for  the  molybdate  pre- 


EXAMINATION  OF  COMMERCIAL  FERTILIZERS     131 

cipitation  in  the  manner  above  indicated,  thus 
determining  the  water-soluble  phosphoric  acid 
directly,  or  it  may  be  determined  indirectly  by 
igniting  the  filter  and  contents  and  determining 
the  phosphoric  acid  insoluble  in  water  by  the 
method  prescribed  for  "total."  In  that  case 
use  the  whole  solution  from  the  residue  for  the 
determination.  The  "water  soluble"  will  then 
be  found  by  difference. 

Citrate  Soluble  Phosphoric  Acid. — Take  2  gms., 
wash  out  the  "water  soluble"  as  before,  and 
then  rinse  the  residue  into  a  200  cc.  flask  by  use 
of  100  cc.  of  absolutely  neutral  ammonium  cit- 
rate solution  of  sp.gr.  1 .09.  Cork  the  flask,  immerse 
it  in  water  at  65°  and  keep  it  at  that  tempera- 
ture for  exactly  30  minutes;  then  filter  rapidly, 
and  wash  with  water  of  about  the  same  tempera- 
ture. The  "reduced"  phosphoric  acid  is  by  this 
means  removed.  It  will,  however,  be  more  con- 
venient to  determine  it  indirectly  by  igniting 
the  filter-paper  and  contents,  and  carrying 
through  the  determination  on  the  portion  un- 
dissolved,  which  really  constitutes  the  "  insoluble 
phosphoric  acid. 

Ammonium  tartrate  and  also  ammonium  ox- 
alate,  have  been  used  in  place  of  the  ammonium 
citrate,  but  the  results  with  those  salts  have  been 
found  irregular  and  unsatisfactory,  and  their 
use  has  been  practically  abolished.  Especial 
care  is  necessary  to  have  the  citrate  solution 
absolutely  neutral — a  result  not  attained  by  dis- 


132     MANUFACTURE  OF  FERTILIZING  MATERIALS 

solving  the  ammonium  citrate  obtained  from 
dealers  in  water. 

Nitrogen. — The  absolute  method  for  nitro- 
gen consists  in  mixing  the  sample  of  fertilizer 
with  copper  oxide,  and  then  heating  to  redness 
*  in  a  tube.  The  carbon  and  hydrogen  take  oxy- 
gen from  the  copper  oxide  becoming  carbon 
dioxide  and  water,  while  the  nitrogen  is  set  free 
in  the  gaseous  form.  Copper  oxide  is  intro- 
duced on  both  sides  of  the  mixture  or  sample 
of  fertilizer  with  the  oxide  in  order  to  thor- 
oughly burn  up  any  volatile  portions  coming  from 
the  sample.  In  order  to  destroy  any  nitrogen 
oxides  which  may  be  present  or  be  found  during 
the  combustion,  metallic  copper,  preferably  in 
the  form  of  a  roll  of  wire  gauze,  is  interposed 
in  the  path  of  the  gases  to  the  azotometer,  the 
function  of  which  is  to  abstract  the  oxygen  from 
the  nitrogen  oxides  under  the  conditions  produced. 

It  has  been  often  found  that  the  copper 
gauze  does  more  than  is  intended,  and  abstracts 
some  oxygen  from  the  carbon  dioxide  as  well, 
giving  small  amounts  of  carbon  monoxide;  so 
to  remedy  this  a  third  layer  of  copper  oxide  is 
interposed,  which  will  reoxidize  it  to  carbon 
dioxide. 

To  remove  the  air  from  the  tube  at  the  be- 
ginning of  the  operation,  the  extreme  end  of  the 
tube  is  charged  with  coarsely  crushed  carbonate, 
which  on  heating  evolves  carbon  dioxide,  and 
sweeps  the  air  from  the  tube  before  the  combus- 


EXAMINATION  OF  COMMERCIAL  FERTILIZERS     133 

tion  is  actually  begun.  The  magnesium  car- 
bonate is  again  heated  at  the  close  of  the  opera- 
tion to  drive  the  nitrogen  remaining  in  the  tube 
into  the  azotometer. 

The  azotometer  is  a  graduated  tube,  with 
stop-cock  above  and  two  side  tubes  below,  at 
different  heights.  The  lower  part  of  the  azo- 
tometer as  well  as  the  lower  side  tube  is  filled 
with  mercury.  The  upper  side  tube  and  the  re- 
mainder of  the  azotometer  is  filled  (when  ready 
for  use)  with  a  strong  solution  of  caustic  potash 
(to  absorb  carbon  dioxide).  The  upper  side  tube 
is  connected  with  a  stop-cock  bulb  containing 
the  caustic  alkali.  The  bulb  is  supported  in 
such  a  way  that  it  can  be  raised  and  lowered 
at  will. 

The  copper  oxide  should  be  ignited  and 
cooled  before  using.  The  portion  which  is  to  be 
mixed  with  the  substance  must  be  ground  in 
a  mortar  until  it  is  reduced  to  a  fine  sand. 

Select  a  tube  of  good  hard  glass  which  is 
sealed  at  one  end  of  a  length  of  about  24  to  27 
in.  Charge  as  follows: 

Magnesium  carbonate,  crushed  to  pieces  four 
or  five  times  the  size  of  a  pin's  head,  1J  to  2  in. 

Coarse    granular    copper  oxide,    1|  to    2    in. 

Fine  copper  oxide  mixed  with  the  substance, 
4  in.  0.5  to  2  gms.  of  the  fertilizer  substance 
are  weighed  out  in  a  watch-glass,  then  mixed 
with  copper  oxide,  and  poured  into  the  tube  by 
the  aid  of  a  small  paper  scoop  or  funnel.  A 


134    MANUFACTURE  OF  FERTILIZING  MATERIALS 

little  more  of  the  fine  copper  oxide  is  then  used 
to  rinse  off  the  watch-glass,  the  whole  amount 
being  just  about  sufficient  to  fill  the  tube  loosely 
without  shaking  down  to  the  depth  of  about 
4  in. 

Coarse   granular   copper   oxide,    about   8   in. 

Metallic  copper,  preferably  in  the  form  of 
a  closely  rolled  coil  of  fine  wire  gauze,  3  in. 

Coarse    granular    copper    oxide    about    2    in. 

Asbestos  plug. 

Lay  the  tube  so  charged  in  the  trough  of  a 
combustion  furnace  and  fit  tightly  into  the  open 
end  a  rubber  stopper  carrying  a  glass  tube  con- 
nected by  means  of  a  rubber  tube  with  another 
tube  dipping  into  the  mercury  in  the  azotometer. 

The  end  carrying  the  rubber  stopper  should 
project  from  the  furnace  far  enough  to  avoid 
charring  the  rubber. 

Then  heat  up  the  magnesium  carbonate, 
starting  cautiously  at  first  so  as  not  to  break  the 
tube.  The  air  in  the  tube  is  thus  driven  in  to 
the  azotometer.  When  the  bubbles  of  gas  rising 
through  the  mercury  are  completely  absorbed 
by  the  caustic  alkali  in  the  upper  part  of  the 
azotometer,  heat  up  the  copper  oxide  at  the  other 
end  of  the  tube,  using  the  same  caution  as  before, 
carrying  the  heat  slowly  back  until  the  metallic 
copper  as  well  as  a  couple  of  inches  of  the  cop- 
per oxide  on  each  side  of  it  is  at  a  full  red  heat. 
Lower  the  heat  on  the  magnesium  carbonate, 
pinch  the  rubber  connection  between  the  com- 


EXAMINATION  OF  COMMERCIAL  FERTILIZERS     135 

bustion  tube  and  the  azotometer  for  a  moment, 
open  the  upper  stop-cock  of  the  azotometer, 
and  by  raising  the  bulb  force  the  gas  out  of  the 
azotometer.  Close  the  azometer  stop-cock  and 
release  the  connection.  Then  carry  the  heat 
slowly  back  to  the  mixture  of  the  substance  or 
fertilizer  with  the  copper  oxide,  getting  all  of 
the  tube  except  the  magnesium  carbonate  end 
finally  up  to  full  red  heat.  The  progress  of  the 
combustion  may  be  judged  by  the  rapidity  with 
which  the  bubbles  of  gas  pass  through  the  mer- 
cury. It  should  not  be  faster  than  about  two 
bubbles  per  second. 

When  they  cease,  heat  up  the  magnesium 
carbonate  again,  keeping  up  the  heat  until  the 
gas  driven  from  the  tube  is  all  absorbed  by  the 
caustic  alkali.  Then  disconnect  the  azotometer, 
and  cool  down  the  tube.  Allow  the  azotometer 
to  stand  for  some  time  to  cool  completely,  and 
hang  it  near  a  thermometer.  Bring  the  bulb 
close  to  the  azotometer,  and  raise  or  lower  it 
until  the  level  of  the  solution  in  both  is  the  same. 
Then  read  the  volume  of  the  gas  and  the  tem- 
perature, and  calculate  the  weight  of  the  nitrogen. 

When  not  in  use  the  azotometer  should  be 
washed  free  from  caustic  alkali,  especially  as  to 
the  stop-cock,  which  should  always  be  taken 
out,  wiped  off,  and  freshly  lubricated  with  a 
little  vaseline. 

Potassium. — Weigh  out  10  gms.  of  fertilizer 
material,  Dissolve  in  a  porcelain  evaporating 


136     MANUFACTURE  OF  FERTILIZING  MATERIALS 

dish  with  as  little  water  as  convenient,  and  let  boil 
for  30  minutes.  Then  render  alkaline  with  am- 
monia, and  add  ammonium  oxalate  in  quantity 
sufficient  to  precipitate  all  the  lime,  cool,  and 
make  up  to  500  cc.  and  mix  well.  Filter  and  take 
of  the  filtrate  lots  of  25  or  50  cc.  according  to 
requirements.  Evaporate  these  down  in  plat- 
inum dishes  after  acidifying  with  sulphuric  acid, 
finally  igniting  the  residue  until  white.  Dissolve 
in  a  little  water,  which  should  give  a  clear  solution; 
acidify  with  a  drop  or  two  of  hydrochloric  acid; 
add  5  cc.  of  platinum  chloride,  evaporate  to  a 
pasty  condition;  add  30  cc.  or  more  of  strong 
alcohol  (80  per  cent  or  over),  allow  to  stand 
cold  for  some  time,  and  then  decant  on  weighed 
filter  and  add  fresh  alcohol,  and  repeat  two 
or  three  times,  and  then  transfer  to  filter  and 
wash  with  ether;  dry,  cool  in  desiccator,  and 
weigh.  From  total  weight  deduct  weight  of 
filter-paper,  or  a  Gooch  crucible  with  asbestos 
filter  may  be  used.  Precipitate  is  K^PtCle. 
In  place  of  alcohol  a  mixture  of  alcohol  and 
ether  is  preferable  in  proportions  of  2  to  1. 

Regarding  the  examination  of  phosphatic  ma- 
terials to  be  used  in  the  manufacture  of  fertili- 
zers, a  few  suggestions  may  be  desirable. 

Spent  bone-black  and  other  materials  con- 
taining carbon  or  carbonaceous  material  as  well 
as  phosphate  rock,  may  be  ignited  to  burn  off 
the  organic  substances,  then  dissolved  in  hydro- 
chloric acid,  and  in  general  treated  essentially 


EXAMINATION  OF  COMMERCIAL  FERTILIZERS     137 

as  recommended  for  the  determination  of  total 
phosphoric  acid. 

With  phosphatic  slags  the  first  hydrochloric 
acid  solution  should  be  evaporated  to  dryness 
in  order  to  remove  the  silica  (which  would  other- 
wise appear  in  gelatinous  form).  Before  pro- 
ceeding with  phosphate  rock,  the  proportion  of 
iron  and  alumina  oxides  is  of  much  importance 
on  account  of  their  tendency  to  afford  the  so- 
called  "reduced  phosphate"  in  the  finished  prod- 
uct. A  good  method  consists  in  dissolving  the 
sample  in  aqua  regia,  adding  sulphuric  acid, 
and  then  a  large  excess  of  alcohol,  which  pre- 
cipitates the  calcium  sulphate.  In  the  clear 
alcoholic  solution  the  iron  and  alumina,  as 
phosphates,  may  be  determined. 

Another  plan  affording  good  results  when 
carefully  conducted  would  be  to  dissolve  2.5 
gms.  of  the  material  in  10  cc.  of  hydrochloric 
acid  and  1  or  2  cc.  of  nitric  acid.  Then  add  10 
cc.  of  concentrated  sulphuric  acid,  mix  in  well, 
and  add  strong  alcohol,  90  per  cent  or  over, 
in  sufficient  quantity  to  bring  the  bulk  of  the 
solution,  when  well  mixed  and  cold,  up  to  250 
cc.  Shake  well,  and  allow  to  settle  for  30  to  60 
minutes.  Then  filter  off  rapidly  200  cc.  (represent- 
ing 2  gms.),  neutralize  very  exactly  with  am- 
monia, boil  out  the  alcohol,  avoiding  evapora- 
tion to  dryness,  and  then  render  alkaline  with 
a  little  ammonia,  boil  and  filter.  The  precipitate, 
consisting  of  iron  and  alumina  phosphate,  is 


138    MANUFACTURE  OF  FERTILIZING  MATERIALS 

ignited  and  weighed  by  some,  and  half  its  weight 
taken  as  that  of  the  iron  alumina  oxide,  which 
roughly  speaking  is  true.  It  is,  however,  more 
exact  and  satisfactory  to  dissolve  the  moist, 
hydrates  in  nitric  acid,  neutralize  closely,  pre- 
cipitate out  phosphoric  acid  with  a  sufficient 
but  not  too  large  excess  of  ammonium  molyb- 
date,  letting  it  stand  warm  for  some  hours, 
and  in  the  filtrate  precipitate  with  ammonia, 
boiling  out  the  excess  to  render  the  alumina 
insoluble.  Filter,  and  then  treat  the  precipitate 
with  about  10  cc.  of  strong  ammonia  to  dissolve 
out  the  molybdic  acid,  wash  again,  and  dry, 
ignite,  and  weigh  the  mixed  oxides. 

If  desired,  the  precipitate  may  be  brought 
into  solution,  and  the  iron  reduced  and  titrated 
in  the  usual  manner,  the  alumina  being  obtained 
by  difference. 


CHAPTER  XIV 
ON  THE  EXAMINATION   OF   SOILS 

SURFACE  accumulations  of  decaying  leaves 
should  be  removed  and  a  slice  of  uniform  thick- 
ness from  the  surface  to  the  desired  depth  should 
be  secured.  To  eliminate  the  effects  of  accidental 
variations  in  the  soil,  select  specimens  from  five 
or  six  places  in  the  field  and  remove  several 
pounds  of  the  soil  to  the  depth  of  six  inches,  or  to 
the  change  between  the  surface  soil  and  the  sub- 
soil, in  case  such  change  occurs  between  the 
depth  of  six  and  twelve  inches.  In  no  case  is 
the  sample  to  be  secured  to  a  greater  depth  than 
twelve  inches.  If  the  surface  soil  extend  to  a 
greater  depth,  a  separate  sample  below  the  depth 
of  12  inches  is  to  be  obtained.  If  the  surface 
soil  extend  to  a  depth  of  less  than  6  inches,  and 
the  difference  between  it  and  the  subsoil  is 
usually  great,  a  separate  sample  of  the  surface 
soil  should  be  secured,  besides  the  one  to  the 
depth  of  six  inches. 

The  depth  to  which  the  sample  of  subsoil 
should  extend  will  depend  on  circumstances. 
It  is  always  necessary  to  know  what  constitutes 
the  foundation  of  a  soil,  to  the  depth  of  three 
feet  at  least,  since  the  question  of  drainage, 

139 


140     MANUFACTURE  OF  FERTILIZING  MATERIALS 

resistance  to  drought,  etc.,  will  depend  essentially 
upon  the  nature  of  the  substratum.  But  in  or- 
dinary eases  10  or  12  in.  of  subsoil  will  be  suf- 
ficient for  the  purposes  of  examination  in  the 
laboratory.  The  specimen  should  be  obtained  in 
other  respects  precisely  like  that  of  the  surface 
soil,  while  that  of  i?he  material  underlying  this 
subsoil  may  be  sampled  with  less  exactness, 
perhaps  at  some  ditch  or  other  easily  accessible 
point,  and  should  not  be  broken  up,  but  left,  as 
nearly  as  possible,  in  its  original  state.  Mix  each 
of  these  soils  intimately,  remove  any  stones,  shake 
out  all  roots  and  foreign  matter,  expose  in  thin 
layers  in  a  warm  room  till  thoroughly  air-dry, 
or  dry  in  an  air-bath  at  a  temperature  of  40°  C. 

The  soil  is  rapidly  dried  to  arrest  nitrifi- 
cation. It  is  not  heated  above  40°  lest  there  be  a 
dissipation  of  ammonium  compounds,  or  a  change 
in  the  solubility  of  the  soil.  The  normal  limit 
to  which  the  soil  may  be  heated  in  place  by  the 
sun's  rays  should  not  be  exceeded  in  preparing 
a  soil  for  an  agricultural  chemical  analysis. 

Five  hundred  gms.  or  more  of  the  air-dried 
soil,  which  may  be  either  the  original  soil  or 
that  which  has  been  passed  through  a  sieve  of 
coarser  mesh,  are  sifted  through  a  sieve  with 
circular  openings  one-half  millimeter  in  diameter, 
rubbing,  if  necessary,  with  a  rubber  pestle  in 
a  mortar  until  the  fine  earth  has  been  separated 
as  completely  as  possible  from  the  particles 
that  are  too  coarse  to  pass  the  sieve.  A  three- 


ON  THE  EXAMINATION  OF  SOILS  141 

millimeter  sieve  should  be  used  when  the  de- 
terminations are  made  on  100  gms.  or  more  of 
soil.  The  fine  earth  is  thoroughly  mixed  and 
preserved  in  a  tightly  stoppered  bottle,  from 
which  the  portions  for  analysis  are  weighed. 

The  coarse  part  is  weighed  and  examined 
microscopically  or  with  Thoulet's  solution. 

It  may  sometimes  be  necessary  to  wash  the 
soil  through  the  one-half  millimeter  sieve  with 
water;  but  this  is  to  be  avoided  whenever  possible. 

Determination  of  Moisture. — Heat  from  2  to 
5  gms.  of  the  air-dried  soil  in  a  flat-bottom, 
tared  platinum  dish  for  five  hours  in  a  water 
oven  kept  briskly  boiling;  cover  the  dish,  cool 
in  a  desiccator,  and  weigh.  Repeat  the  heating, 
cooling,  and  weighing  at  intervals  of  two  hours 
till  nearly  constant  weight  is  found,  and  estimate 
the  moisture  by  the  loss  of  weight.  Weigh  rapidly, 
to  avoid  absorption  of  moisture  from  the  air. 

Determination  of  Volatile  Matter.— Heat  the 
dish  and  dry  soil  from  the  above  determination 
to  full  redness,  until  all  organic  matter  is  burned 
away.  If  the  soil  contains  appreciable  quantities 
of  carbonates,  the  contents  of  the  dish,  after 
cooling,  are  moistened  with  a  few  drops  of  a 
saturated  solution  of  ammonium  carbonate,  dried 
and  heated  to  dull  redness  to  expel  salts  of 
ammonia,  cooled  in  a  desiccator,  and  weighed. 
The  loss  in  weight  represents  the  organic  matter, 
water  of  combination,  salts  of  ammonium. 

Determination  of  Acid-soluble  Materials. — In  the 


142     MANUFACTURE  OF  FERTILIZING  MATERIALS 

following  scheme  for  soil  analysis  it  is  in- 
tended to  use  the  air-dried  soil  from  the  sample 
bottle  for  each  separate  investigation.  The  de- 
termination of  moisture,  made  once  for  all  on 
a  separate  portion  of  air-dried  soil,  will  afford 
the  datum  for  calculating  the  results  of  analysis 
upon  the  soil  dried  at  the  temperature  of  boil- 
ing water.  It  is  not  desirable  to  ignite  the  soil 
before  analysis,  or  to  heat  it  so  as  to  change 
its  chemical  properties. 

The  acid  digestion  is  to  be  performed  in  a 
flask  so  arranged  that  evaporation  of  acid  shall 
be  reduced  to  a  minimum,  but  under  atmos- 
pheric pressure  and  at  the  temperature  of  boil- 
ing water.  The  digestion  is  easily  accomplished 
in  a  flat-bottom  conical  flask  of  hard  glass,  Car- 
rying a  stopper  and  hard-glass  condensing  tube 
at  least  18  in.  long.  Where  sulphuric  acid  is 
to  be  determined  a  rubber  stopper  cannot  be 
used.  A  flask  with  ground-glass  stopper,  carrying 
a  condensing  tube,  is  useful  in  such  cases. 

The  flask  must  be  immersed  in  the  water- 
bath  up  to  the  neck,  or  at  least  to  the  level  of 
the  acid,  and  the  water  must  be  kept  boiling 
continuously  during  the  digestion. 

In  the  following  scheme  10  gms.  of  soil  are 
used,  this  being  a  convenient  quantity  of  most 
soils,  in  which  the  insoluble  matter  is  about 
80  per  cent.  If  desired,  a  larger  quantity  of 
such  soil  may  be  used,  with  a  proportionately 
larger  quantity  of  acid,  and  making  up  the  soil 


ON  THE  EXAMINATION  OF  SOILS  143 

solution  to  a  proportionately  larger  volume. 
In  very  sandy  soils,  where  the  proportion  of  in- 
soluble matter  is  90  per  cent  or  more,  20  gms. 
of  soil  are  to  be  digested  with  100  cubic  centi- 
meters of  acid  and  the  solution  made  up  to  500 
cc.;  or  a  larger  quantity  may  be  used,  preserving 
the  same  proportions.  It  is  very  important  that 
the  analyst  assure  himself  of  the  purity  of  all 
the  reagents  to  be  used  in  the  analysis  of  soils 
before  beginning  the  work. 

In  a  flask  of  200  cc.  capacity  place  10  gms. 
of  air-dried  soil  and  100  cc.  of  hydrochloric  acid. 
Close  flask  with  cork,  carrying  a  glass  tube 
about  2  ft.  in  length  to  act  as  reflux  condenser. 
Place  flask  in  water-bath  and  keep  at  boiling 
temperature  for  ten  hours  with  occasional  shak- 
ing. Transfer  contents  of  flask  to  a  beaker,  and 
bring  residue  on  to  filter  and  wash  with  distilled 
water;  dry  residue  and  weigh  as  insoluble  ma- 
terial. Make  solutions  and  washings  up  to  500 
cc.  with  distilled  water. 

Iron  and  Alumina. — 100  cc.  of  above  solution 
are  made  slightly  alkaline  with  ammonia,  then 
boiled  to  expel  excess  of  ammonia,  filtered, 
and  well  washed  with  hot  distilled  water.  The 
precipitate  is  iron,  alumina  and  phosphates. 
After  drjdng,  igniting  in  tared  crucible,  and 
weighing  the  desiccated  product,  the  iron  and 
alumina  may  be  separated  as  follows:  Bring 
residue  of  iron  and  alumina  into  a  beaker,  add  15 
cc.  of  dilute  sulphuric  acid  (1  of  acid  and  4  of 


144     MANUFACTURE  OF  FERTILIZING  MATERIALS 

water),  heat  on  water-bath  with  beaker  covered 
until  in  solution,  then  determine  iron  with  po- 
tassium permanganate  by  volumetric  method, 
and  from  these  results  and  total,  iron  and  alu- 
minium phosphate  estimate  the  amount  of  iron 
and  alumina. 

Manganese. — The  filtrate  above  is  concentrated 
to  about  100  cc.,  ammonia  added  to  alkalinity, 
bromine  water  added  and  the  solution  heated 
to  boiling.  Allow  the  solution  to  cool  and 
add  more  bromine  water  and  ammonia,  and 
heat  as  before  to  precipitate  all  the  mangan- 
ese; acidify  with  acetic  acid,  and  filter  while 
still  boiling,  wash  with  hot  water  and  ignite 
as  manganous  manganic  ioxide,  Mn3O4. 

Calcium. — Evaporate  above  filtrate  to  about 
50  cc.,  add  ammonia  to  slight  alkalinity,  and  to 
the  hot  solution  add  ammonium  oxalate  and 
allow  to  stand  twelve  hours,  filter,  and  wash  with 
hot  water  containing  a  little  ammonia;  dry, 
and  transfer  precipitate  to  tared  platinum  cru- 
cible; burn  filter-paper,  add  ash  to  the  crucible, 
and  ignite,  at  first  slowly  and  finally  with  full 
blast;  cool,  and  weight  as  calcium  oxide. 

Magnesia. — If  necessary  concentrate  the  fil- 
trate above,  make  alkaline  with  ammonia, 
add  Na2HPO4  until  no  further  precipitate  occurs, 
stir  carefully  without  touching  sides  of  beaker, 
and  allow  to  stand  until  solution  above  precipi- 
tate is  perfectly  clear.  Filter  and  wash  out 
beaker  with  portions  of  the  filtrate,  and  then 


ON  THE  EXAMINATION  OF  SOILS  145 

wash  with  diluted  ammonia  water  (1  part  am- 
monia to  8  parts  water)  until  filtrate  gives  no 
coloration  with  nitric  acid  and  silver  nitrate. 
Dry  thoroughly,  remove  precipitate  to  tared 
porcelain  crucible,  burn  filter-paper  and  add  the 
ash  to  the  crucible  and  its  contents,  and  ignite, 
at  first  slowly,  then  to  intense  heat;  cool,  and 
weigh  as  Mg2P2O?. 

Alkalies. — To  the  last  filtrate  add  ammonia, 
boil  to  expel  excess  of  ammonia,  filter  and  wash. 
Evaporate  the  filtrate  to  dryness,  heat  below 
redness  to  expel  ammonia  salts,  add  30  cc.  of 
water,  then  a  few  drops  of  barium  hydroxide  so- 
lution, and  heat  to  boiling.  Filter  and  wash 
with  hot  water.  To  the  filtrate  add  ammonia 
hydroxide  and  ammonium  carbonate,  filter,  and 
wash  with  hot  water.  Evaporate  to  dryness  and 
determine  potassium  by  adding  platinic  chloride 
to  slight  excess,  and  evaporate  almost  to  dry- 
ness  on  water-bath;  then  add  40  cc.  of  80  per 
cent  alcohol,  and  allow  to  stand  for  one  hour; 
then  decant  on  weighed  filter  and  add  fresh 
alcohol,  and  repeat  two  or  three  times,  and  then 
transfer  to  filter  and  wash  with  ether;  dry,  cool 
in  desiccator,  and  weigh.  From  total  weight 
deduct  weight  of  filter-paper,  or  a  Gooch  crucible 
with  asbestos  filter  may  be  used.  Precipitate 
is  potassium  platinic  chloride.  In  place  of  alcohol 
a  mixture  of  alcohol  and  ether  is  preferable  in 
proportion  of  2  and  1. 

Sodium. — The  mixed  alkalies  are  weighed  as 


146     MANUFACTURE  OF  FERTILIZING  MATERIALS 

chlorides,  the  solution  having  been  evaporated  to 
dryness  and  the  ammonium  salts  expelled  by  heat- 
ing to  dull  redness.  Dissolve  the  precipitate  with 
10  cc.  of  water  and  add  platinic  chloride  as  in 
potash  determination,  precipitating  potash  and 
sodium.  After  evaporating  dissolve  the  sodium 
platinic  chloride  out  with  alcohol,  leaving  potas- 
sium platinic  chloride  to  be  dried  and  weighed  for 
the  potash  determination.  The  sodium  can  be 
determined  by  difference  of  the  total  weight  of 
alkalies. 

Carbon  Dioxide. — In  five  grams  of  the  air- 
dried  soil  determine  carbon  dioxide  by  mixing 
with  about  four  times  its  weight  of  powdered 
borax,  and  fuse.  Weigh  and  the  loss  in  weight 
can  be  taken  as  carbon  dioxide. 

Nitrogen. — Of  the  air-dried  soil  weigh  out 
three  grams,  place  in  a  digestion  flask,  add  30 
cc.  of  concentrated  sulphuric  acid  (sp.gr.  1.84) 
containing  one  gram  of  salicylic  acid,  and  thor- 
oughly mix  by  shaking.  Heat  over  a  low  flame 
until  no  further  frothing,  and  then  boil  briskly 
for  five  or  ten  minutes;  now  add  about  0.7  gram 
of  mercuric  oxide,  and  continue  the  boiling  until  the 
solution  is  colorless;  then  complete  the  oxidation 
by  adding  slowly  fine  pulverized  potassium  per- 
manganate to  the  hot  solution,  until  after  shaking 
the  solution  is  green  or  purple  in  color.  Transfer 
the  contents  of  the  cool  flask  to  a  distilling  flask, 
using  about  100  cc.  of  water,  and  add  a  few 
pieces  of  granulated  zinc  to  prevent  bumping; 


ON  THE  EXAMINATION  OF  SOILS  147 

now  add  30  cc.  of  potassium  sulphide  solution 
(40  grams  in  1000  cc.  water),  and  after  shaking 
add  80  cc.  of  a  saturated  caustic  soda  solution  or 
enough  to  make  it  alkaline.  Connect  at  once  with 
the  condenser,  and  distill  over  about  125  cc.,  receiv- 
ing into  a  measured  quantity  of  standard  acid,  and 
then  titrate  with  standard  alkali,  using  cochineal 
as  indicator.  One  cc.  of  the  decinormal  sulphuric 
acid  is  equal  to  .0014  gram  of  nitrogen. 

In  the  absence  of  nitrates  the  salicylic  acid 
may  be  omitted  from  the  sulphuric  acid;  other- 
wise the  nitrogen  determination  is  made  the 
same  way  as  above,  with  varying  amount  of 
substances  to  be  analyzed,  according  to  its 
nitrogen  content. 

Phosphoric  Acid. — Ten  grams  of  the  sifter  soil, 
dried  at  100°  C.,  are  charred  if  organic  matter 
be  present.  The  charred  mass  is  moistened  with 
water  and  afterwards  with  nitric  acid,  until 
the  carbonates  are  decomposed.  The  mass  is 
digested  with  ten  cubic  centimeters  of  nitric 
acid  for  two  hours  at  about  100°  C.  with  fre- 
quent stirrings  and  the  addition  of  fresh  acid, 
from  time  to  time,  to  replace  that  which  has 
been  evaporated.  After  filtering  and  washing 
with  hot  water  the  filtrate  is  evaporated  to  a 
volume  of  50  cc.  and  treated  with  five  cubic 
centimeters  of  concentrated  nitric  acid  and  half 
a  gram  of  crystals  of  chromic  acid.  After  covering 
the  dish  with  a  funnel  to  return  condensed 
vapors  its  contents  are  heated  to  the  boiling 


148     MANUFACTURE  OF  FERTILIZING  MATERIALS 

point  for  half  an  hour  to  complete  the  destruc- 
tion of  organic  matter.  At  the  end  of  this  time 
five  grams  of  ammonium  nitrate  are  added  to 
facilitate  the  precipitation  of  the  phosphoric 
acid,  and  50  cc.  of  molybdate  solution,  and  the 
mixture  kept  at  a  temperature  of  about  100°  C. 
for  an  hour.  The  precipitate  obtained  is  washed 
twice  by  decantation  with  water  containing 
one-fifth  of  its  volume  of  ammonium  molybdate 
solution.  It  is  dissolved  in  30  cc.  of  ammonia 
diluted  with  an  equal  bulk  of  warm  water.  The 
solution  and  washings  should  measure  80  cc. 
and  the  ammonia  therein  is  neutralized  with 
nitric  acid,  keeping  the  temperature  below  40°  C. 
When  the  yellow  precipitate  formed  ceases  to 
redissolve  on  stirring,  that  is,  when  the  ammonia 
has  been  neutralized,  a  mixture  of  3  cc.  of 
pure  nitric  acid  and  5  cc.  of  water  is  added, 
together  with  the  same  quantity  of  molybdate 
solution.  After  standing  for  two  hours  at  40°  C. 
the  precipitate  is  brought  upon  a  filter,  washed 
first  with  water  containing  1  per  cent  of  nitric 
acid,  and  finally  with  a  little  pure  water,  and 
dried  at  100°  C.  and  weighed.  The  weight  of 
the  precipitate  multiplied  by  the  factor  0.0373 
gives  the  quantity  of  phosphoric  acid.  The 
object  of  the  second  precipitation  is  to  relieve  the 
process  of  the  necessity  of  rendering  the  silica 
insoluble,  as  the  presence  of  silica  in  the  solu- 
tion as  above  treated  does  not  interfere  with 
the  complete  precipitation  of  the  phosphate. 


INDEX 


Acid,  humic,  99 
hydrochloric,  128 
phosphoric,  5,  7,  8,  63,  83, 

127,  128,  130,  131,  147 
soluble  materials  in  soils, 

determination  of,  141 
sulphuric,  56,  60,  62,  75 
Alkalis,  determination  of,  in 

soils,  145 

Aluminum,  17,  23,  61 
Ammoniated      superphos- 
phate, 78 

Ammonium,  5,  6,  7 
oxalate,  131 
sulphate,  56,  78,  79,  84,  87, 

99 

tartrate,  131 
Analysis  of  fertilizers,  126 

of  soils,  139 
Apatite,  22 

Artificial    manure    manufac- 
ture, 60 

Available  phosphoric  acid,  8 
Azotometer,  133 


* 


B 


Barium,  17, 29 

Basic  slag,  55 

Birkeland  and  Eyde  process, 
96 

Blackmore,  H.  S.,  a  method 
for  producing  soluble 
potash  salts  from  feld- 
spar, 113 

Bone  meal,  55 

Borax,  23 

Boren,  23 

Burnt  lime,  11 


Cabbage,  32 

Calcium,  2,  13,  17,  24,  25 

cyanamide,  98 

determination    of  in  soils 
144 

oxide,  11 
Caliche,  57,  89 
Carbon,  17,  19 

dioxide,  determination  of, 

.    in  soils,  146 


149 


150 


INDEX 


Carnellite,  58  102 

Chemistry  of  fertilizers,  I 

Chili  saltpeter,  28,  57,  88 

Chrominium,  17,  29 

Chlorine,  17,  21 

Chromium,  29 

Citrate  soluble  phosphoric 
acid,  131 

Clays,  24,  43 

Compound  manures,  77 

Corn,  32  | 

Cushman,  A.  S.,  patent  for 
obtaining  potash  from 
silicate  rocks,  115 

Cyanamide,  manufacture  of, 


95,98 


D 


Denitrifying  organism,  13 
Dicyanamide,  98 
Direct  fertilizers,  2,  14 
Dolomite,  26 
Double  rock  washer,  53 
Dredge  boat  dredging,  44 
Drying  shed,  48,  81 

E 

Edge  runners,  68 
Elements,  17 


Feldspar,  19,  113 
manufacture    of    manure 
from,  101 


Fertilizers,  chemistry  of,  1 

direct,  2,  14 

examination  of,  126 

indirect,  11 
Flat  stone  mills,  68 
Floating  dredge  boat,  48 
Flourine,  17,  23 
Fixation  of  Nitrogen,  95 
Frank  and  Caro  process,  96 


Geber,  87 
Grass,  32 
Grizzeles,  46 
Guano,  58 
Gypsum,  11,20 


II 


Hard  rock  phosphate,  mill, 

49 
ore  dressing   and   milling, 

43 

Herpath,  87 
Humus,  19 
Hydraulic  mining,  38,  39 

nozzles,  40 
Hydrogen,  17,  21 


Indian  saltpeter,  89 
Indirect  fertilizer,  11 
Insoluble  phosphoric  acid,  8 


INDEX 


151 


Iron,  17, 28 

and    alumina,    determina- 
tion of,  in  soils,  143 
pyrites,  20 

K 

Kainit,  58 
Kelp,  124, 125 

manufacture    of     manure 

from,  101 
Kieserite,  102 


Land-pebble  phosphate,  37 

-plaster,  11 
Laws,  fundamental,  1 
Lime,  4 

M 

Magnesium,  25 

determination  of,  in  soils, 
144 

Manganese,  29 
determination  of,  in  soils, 
144 

Manufacture  of  superphos- 
phate, 67 

Manures,  58 

Marcus,  87 

Marquinas,  91 

McKee,  Ralph  H.,  patent  for 
obtaining  potassium 
compounds  from  feld- 
spar, 114 


Meal,  bone,  55 
Mill,  hard  rock,  49 
Mineral  phosphates,  61 
Mixing  machine,  70 
Moisture,  in  fertilizers,  126 
determination  of,  in  soils, 
141 


N 

Nitrates,  22 
Nitrate,  of  soda,  84 

of  lime,  manufacture  of,  95 
Nitre,  88 
Nitric  acid,  88 
Nitrifying  organisms,  12 
Nitrites,  12 
Nitrogen,  2,  17,  22,  87 

determination    of,   in   fer- 
tilizers, 132 

determination  of  in  soils, 
146 

fixation  of,  95 
Nitrogenous  manures,  87 
Nitromonas,  12 
Non-exhaustible  elements,  30 
Notodden,  97 


O 


Ore,  phosphate,  37,  43 
Organic  nitrogenous  material, 

58 
Origin  of  soils,  15 

of  phosphate  ore,  52 
Oxygen,  17 


152 


INDEX 


Paradas,  91 

Pebble  phosphate  ore  dress- 
ing and  milling,  37 
Peruvian  guano,  59 
Pfeiffer's  mills,  69 
Phosphate  washer,  41 
Phosphates,  4,  60 
Phosphate    ore,   37,   43,   52, 

90 
Phosphoric  acid,  5,  7 

determination  of,  in  soils, 

147 

in  fertilizers,  127 
Phosphorite,  22 
Phosphorus,  22,  52 
Picking  table,  47,  72 
Portland      cement,      potash 

from,  119 

Potash,  3,  5,  7,  33,  58,  101 
manufacture  of,  from  sun- 
flower plant,  123 
manures,  101 
Potassium,  26 
chloride,  106 

determination  of,  in  fertil- 
izers, 135 
manures,  101 
oxide,  8 
sulphate,  112 
Potatoes,  32 
Precipitated  phosphoric  acid, 

8 

Psilomelane,  29 
Pyrolusite,  29 


Q 


Quartz,  19 
Quick-lime,  11 


R 


Raymond  Lulle,  88 
Redonda  phosphate,  61 
Reverted  phosphate,  65 
Reverted  phosphoric  acid,  8 
Rhoden,    G.    J.,    patent   for 
obtaining  soluble  potas- 
sium from  feldspar,  114 
Rinser,  47,  64 
River-pebble  phosphate,  38 
Roasting  ores,  50,  51 


Sand-rock,  47 
Separator,  46 
Shark's  teeth,  107 
Silicon,  17,  18 

Smith,  J.  Lawrence,  extract- 
ing potash  from  silicate 
rocks,  113 
Sodium,  17,  27,  57 

chloride,  11 

determination  of,  in  soils, 
145 

nitrate,  33,  57 
Soft  ores,  43 
Soils,  15, 139 

examination  of,  139 


INDEX 


153 


Soil,  fertile,  1 
Soluble  phosphate,  65 

phosphoric  acid,  7 

potash, 9 
Stassfurt  salts,  58 
Steam  shovels,  38 
Stimulant  fertilizer,  1 1 
Sub-soil,  16 

Sulphate  of  ammonia,  34,  82 
Sulphur,  17,  20 
Sunflower,    manufacture    of 
manure  from,  101 

plant,  manufacture  of  pot- 
ash from,  123 
Superphosphate  of  ammonia, 

82 
Superphosphates,  61,  62,  67 


Terms  in  analysis,  5 
Titanium,  17,  29 
Total  phosphoric  acid,  8,  128 
Trommel,  48 


Volatile  matter,   determina- 
tion of,  in  soils,  141 

W 
Wad,  29 

Washer,  phosphate,  41,  47, 

53 
Water     soluble     phosphoric 

acid,  130 


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